assize: [13] Like assess, assize comes ultimately from Latin assidēre, which meant literally ‘sit beside someone’ (it was a compound verb formed from the prefix ad- ‘near’ and sedēre ‘sit’, related to English sit). In Old French this became asseeir (modern French has asseoir), of which the past participle was assis.
The feminine form of this, assise, came to be used as a noun ranging in meaning from the very general ‘act of sitting’ or ‘seat’ to the more specific legal senses ‘sitting in judgement’ and ‘session of a court’ (English session comes ultimately from Latin sedēre too). It was the legal usages which passed into English. => session, sit, size
