Hi OP, English spoken during 1300/1400 is known as Middle English; prominent literary examples include Sir Gawain and the Green Knight, and The Canterbury Tales by Geoffrey Chaucer (1343–1400).
Here are few posts discussing Middle English. I've indicated the ones that include links to readings, so you can hear what it sounds like
Would conversational Middle English be that different than Chaucer’s Middle English? - featuring /u/cdesmoulins
How is it that I can mostly read "The Canterbury Tales" in the original, but "Sir Gawain and the Green Knight," written at roughly the same time and in the same country, is mostly unintelligible? - featuring /u/sunagainstgold and several other users in a long conversation on English in this period
If you took an English person from 1314 and an English person from 1114 and got them to talk to each other would they think each other's speech patterns were odd? If "yes" would they still be able to easily understand each other? - featuring /u/popisfizzy and others
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