diminishyoudaoicibaDictYouDict[diminish 词源字典]
diminish: [15] Diminish is a hybrid verb, the result of a marriage between the now obsolete diminue [14] and the virtually obsolete minish [14], both of which meant ‘make smaller’. Diminue came via Old French diminuer from Latin dīminuere ‘break into small pieces’; it was a compound verb formed from the prefix dē- ‘from’ and minuere ‘lessen’ (source of English minute). Minish came via Old French menuiser from Vulgar Latin *minūtiāre, a derivative of Latin minūtus ‘small’; this, bringing the history of diminish full circle, was an adjectival use of the past participle of minuere.
=> minute[diminish etymology, diminish origin, 英语词源]
diminish (v.)youdaoicibaDictYouDict
early 15c., from merger of two obsolete verbs, diminue and minish. Diminue is from Old French diminuer "make small," from Latin diminuere "break into small pieces," variant of deminuere "lessen, diminish," from de- "completely" + minuere "make small" (see minus).

Minish is from Old French menuisier, from Latin minuere. Related: Diminished; diminishes; diminishing.