As far as I know, he didn't. He called the chained block structure a Timestamp Server in the white paper. Then people came up with Blockchain, which got sullied by shitcoiners, so Bitcoiners rebranded to Timechain and attributed it to Satoshi somehow.
In the v0.1.0 source code Hal Finney sent to mrb on bitcointalk (@zorinaq on twttr), Satoshi
does reference the timechain.
Also numerous references to the timechain in pre-release notes (supposedly from Satoshi sent to ppl who requested them in Nov 2008) posted by Cryddit on bitcointalk, but since I can’t verify those I won’t post them here yet. 
