diff --git a/substrate/client/consensus/aura/src/lib.rs b/substrate/client/consensus/aura/src/lib.rs
index c538200bb3..a0eed6e353 100644
--- a/substrate/client/consensus/aura/src/lib.rs
+++ b/substrate/client/consensus/aura/src/lib.rs
@@ -257,7 +257,7 @@ pub fn build_aura_worker<P, B, C, PF, I, SO, L, BS, Error>(
 	SyncOracle = SO,
 	JustificationSyncLink = L,
 	Claim = P::Public,
-	EpochData = Vec<AuthorityId<P>>,
+	AuxData = Vec<AuthorityId<P>>,
 >
 where
 	B: BlockT,
@@ -330,7 +330,7 @@ where
 		Pin<Box<dyn Future<Output = Result<E::Proposer, sp_consensus::Error>> + Send + 'static>>;
 	type Proposer = E::Proposer;
 	type Claim = P::Public;
-	type EpochData = Vec<AuthorityId<P>>;
+	type AuxData = Vec<AuthorityId<P>>;
 
 	fn logging_target(&self) -> &'static str {
 		"aura"
@@ -340,15 +340,15 @@ where
 		&mut self.block_import
 	}
 
-	fn epoch_data(
+	fn aux_data(
 		&self,
 		header: &B::Header,
 		_slot: Slot,
-	) -> Result<Self::EpochData, sp_consensus::Error> {
+	) -> Result<Self::AuxData, sp_consensus::Error> {
 		authorities(self.client.as_ref(), &BlockId::Hash(header.hash()))
 	}
 
-	fn authorities_len(&self, epoch_data: &Self::EpochData) -> Option<usize> {
+	fn authorities_len(&self, epoch_data: &Self::AuxData) -> Option<usize> {
 		Some(epoch_data.len())
 	}
 
@@ -356,7 +356,7 @@ where
 		&self,
 		_header: &B::Header,
 		slot: Slot,
-		epoch_data: &Self::EpochData,
+		epoch_data: &Self::AuxData,
 	) -> Option<Self::Claim> {
 		let expected_author = slot_author::<P>(slot, epoch_data);
 		expected_author.and_then(|p| {
@@ -382,7 +382,7 @@ where
 		body: Vec<B::Extrinsic>,
 		storage_changes: StorageChanges<<Self::BlockImport as BlockImport<B>>::Transaction, B>,
 		public: Self::Claim,
-		_epoch: Self::EpochData,
+		_epoch: Self::AuxData,
 	) -> Result<
 		sc_consensus::BlockImportParams<B, <Self::BlockImport as BlockImport<B>>::Transaction>,
 		sp_consensus::Error,
diff --git a/substrate/client/consensus/babe/src/lib.rs b/substrate/client/consensus/babe/src/lib.rs
index aef4785b7b..109e5aade0 100644
--- a/substrate/client/consensus/babe/src/lib.rs
+++ b/substrate/client/consensus/babe/src/lib.rs
@@ -729,7 +729,6 @@ where
 	BS: BackoffAuthoringBlocksStrategy<NumberFor<B>> + Sync,
 	Error: std::error::Error + Send + From<ConsensusError> + From<I::Error> + 'static,
 {
-	type EpochData = ViableEpochDescriptor<B::Hash, NumberFor<B>, Epoch>;
 	type Claim = (PreDigest, AuthorityId);
 	type SyncOracle = SO;
 	type JustificationSyncLink = L;
@@ -737,6 +736,7 @@ where
 		Pin<Box<dyn Future<Output = Result<E::Proposer, sp_consensus::Error>> + Send + 'static>>;
 	type Proposer = E::Proposer;
 	type BlockImport = I;
+	type AuxData = ViableEpochDescriptor<B::Hash, NumberFor<B>, Epoch>;
 
 	fn logging_target(&self) -> &'static str {
 		"babe"
@@ -746,11 +746,7 @@ where
 		&mut self.block_import
 	}
 
-	fn epoch_data(
-		&self,
-		parent: &B::Header,
-		slot: Slot,
-	) -> Result<Self::EpochData, ConsensusError> {
+	fn aux_data(&self, parent: &B::Header, slot: Slot) -> Result<Self::AuxData, ConsensusError> {
 		self.epoch_changes
 			.shared_data()
 			.epoch_descriptor_for_child_of(
@@ -763,7 +759,7 @@ where
 			.ok_or(sp_consensus::Error::InvalidAuthoritiesSet)
 	}
 
-	fn authorities_len(&self, epoch_descriptor: &Self::EpochData) -> Option<usize> {
+	fn authorities_len(&self, epoch_descriptor: &Self::AuxData) -> Option<usize> {
 		self.epoch_changes
 			.shared_data()
 			.viable_epoch(epoch_descriptor, |slot| Epoch::genesis(&self.config, slot))
@@ -823,7 +819,7 @@ where
 		body: Vec<B::Extrinsic>,
 		storage_changes: StorageChanges<<Self::BlockImport as BlockImport<B>>::Transaction, B>,
 		(_, public): Self::Claim,
-		epoch_descriptor: Self::EpochData,
+		epoch_descriptor: Self::AuxData,
 	) -> Result<
 		sc_consensus::BlockImportParams<B, <Self::BlockImport as BlockImport<B>>::Transaction>,
 		sp_consensus::Error,
diff --git a/substrate/client/consensus/slots/src/lib.rs b/substrate/client/consensus/slots/src/lib.rs
index 7c5d5d4a73..6225bbbda1 100644
--- a/substrate/client/consensus/slots/src/lib.rs
+++ b/substrate/client/consensus/slots/src/lib.rs
@@ -101,8 +101,8 @@ pub trait SimpleSlotWorker<B: BlockT> {
 	/// Data associated with a slot claim.
 	type Claim: Send + Sync + 'static;
 
-	/// Epoch data necessary for authoring.
-	type EpochData: Send + Sync + 'static;
+	/// Auxiliary data necessary for authoring.
+	type AuxData: Send + Sync + 'static;
 
 	/// The logging target to use when logging messages.
 	fn logging_target(&self) -> &'static str;
@@ -110,29 +110,28 @@ pub trait SimpleSlotWorker<B: BlockT> {
 	/// A handle to a `BlockImport`.
 	fn block_import(&mut self) -> &mut Self::BlockImport;
 
-	/// Returns the epoch data necessary for authoring. For time-dependent epochs,
-	/// use the provided slot number as a canonical source of time.
-	fn epoch_data(
+	/// Returns the auxiliary data necessary for authoring.
+	fn aux_data(
 		&self,
 		header: &B::Header,
 		slot: Slot,
-	) -> Result<Self::EpochData, sp_consensus::Error>;
+	) -> Result<Self::AuxData, sp_consensus::Error>;
 
-	/// Returns the number of authorities given the epoch data.
+	/// Returns the number of authorities.
 	/// None indicate that the authorities information is incomplete.
-	fn authorities_len(&self, epoch_data: &Self::EpochData) -> Option<usize>;
+	fn authorities_len(&self, aux_data: &Self::AuxData) -> Option<usize>;
 
 	/// Tries to claim the given slot, returning an object with claim data if successful.
 	async fn claim_slot(
 		&self,
 		header: &B::Header,
 		slot: Slot,
-		epoch_data: &Self::EpochData,
+		aux_data: &Self::AuxData,
 	) -> Option<Self::Claim>;
 
 	/// Notifies the given slot. Similar to `claim_slot`, but will be called no matter whether we
 	/// need to author blocks or not.
-	fn notify_slot(&self, _header: &B::Header, _slot: Slot, _epoch_data: &Self::EpochData) {}
+	fn notify_slot(&self, _header: &B::Header, _slot: Slot, _aux_data: &Self::AuxData) {}
 
 	/// Return the pre digest data to include in a block authored with the given claim.
 	fn pre_digest_data(&self, slot: Slot, claim: &Self::Claim) -> Vec<sp_runtime::DigestItem>;
@@ -145,7 +144,7 @@ pub trait SimpleSlotWorker<B: BlockT> {
 		body: Vec<B::Extrinsic>,
 		storage_changes: StorageChanges<<Self::BlockImport as BlockImport<B>>::Transaction, B>,
 		public: Self::Claim,
-		epoch: Self::EpochData,
+		epoch: Self::AuxData,
 	) -> Result<
 		sc_consensus::BlockImportParams<B, <Self::BlockImport as BlockImport<B>>::Transaction>,
 		sp_consensus::Error,
@@ -268,12 +267,12 @@ pub trait SimpleSlotWorker<B: BlockT> {
 			Delay::new(proposing_remaining_duration)
 		};
 
-		let epoch_data = match self.epoch_data(&slot_info.chain_head, slot) {
-			Ok(epoch_data) => epoch_data,
+		let aux_data = match self.aux_data(&slot_info.chain_head, slot) {
+			Ok(aux_data) => aux_data,
 			Err(err) => {
 				warn!(
 					target: logging_target,
-					"Unable to fetch epoch data at block {:?}: {}",
+					"Unable to fetch auxiliary data for block {:?}: {}",
 					slot_info.chain_head.hash(),
 					err,
 				);
@@ -290,9 +289,9 @@ pub trait SimpleSlotWorker<B: BlockT> {
 			},
 		};
 
-		self.notify_slot(&slot_info.chain_head, slot, &epoch_data);
+		self.notify_slot(&slot_info.chain_head, slot, &aux_data);
 
-		let authorities_len = self.authorities_len(&epoch_data);
+		let authorities_len = self.authorities_len(&aux_data);
 
 		if !self.force_authoring() &&
 			self.sync_oracle().is_offline() &&
@@ -309,7 +308,7 @@ pub trait SimpleSlotWorker<B: BlockT> {
 			return None
 		}
 
-		let claim = self.claim_slot(&slot_info.chain_head, slot, &epoch_data).await?;
+		let claim = self.claim_slot(&slot_info.chain_head, slot, &aux_data).await?;
 
 		if self.should_backoff(slot, &slot_info.chain_head) {
 			return None
@@ -351,7 +350,7 @@ pub trait SimpleSlotWorker<B: BlockT> {
 				body.clone(),
 				proposal.storage_changes,
 				claim,
-				epoch_data,
+				aux_data,
 			)
 			.await
 		{