suppletion

noun

sup·​ple·​tion sə-ˈplē-shən 

: the occurrence of phonemically unrelated allomorphs of the same morpheme (such as went as the past tense of go or better as the comparative form of good)

suppletive

sə-ˈplē-tiv 

ˈsə-plə-

adjective

Word History

Etymology

earlier, "making good a deficiency, supplementation," going back to Middle English supplecioun "supplement, recompense," borrowed from Anglo-French & Medieval Latin; Anglo-French suppleciun "supplement, addition," borrowed from Medieval Latin supplētiōn-, supplētiō "filling up, compensation, supplying, provision," going back to Late Latin, "completion, complement," from Latin supplēre "to fill up, complete, raise to its full complement" + -tiōn-, -tiō, suffix of verbal action — more at supply entry 2

First Known Use

1909, in the meaning defined above