Etymology: < Anglo-Norman custom, custome, custum, custumme, costome, costoum, coustom, Anglo-Norman and Old French custume, Anglo-Norman and Old French, Middle French costume, coustome, Anglo-Norman and Middle French coustume (Middle French, French coutume , †coustume ) habitual behaviour, habit (c1100), mode of behaviour which is widely practised and accepted, a convention or tradition (a1140), established usage in law, usage having the force of law (beginning of the 12th cent.; frequently in plural), payment made by a tenant to his or her lord (beginning of the 14th cent. or earlier), tax paid on imported or exported goods (first half of the 14th cent. or earlier), in Anglo-Norman also the office where such an import or export tax is collected (a1346 or earlier), ultimately < classical Latin consuētūdin- , consuētūdō consuetude n. (which is attested in the sense ‘import or export duty’ 1215 in the Magna Carta). Compare costume n., which shows a later borrowing of the same French word.Foreign-language parallels. Compare: (i) Old Occitan costum , Catalan costum (1272), Spanish costumbre (12th cent.), Portuguese costume (second half of the 13th cent.), Italian costume (last quarter of the 12th cent.; probably via Old French or Old Occitan), all masculine (showing change of gender, perhaps after the Romance reflexes of Latin neuter nouns in -ūmen ); (ii) Old Occitan costuma (early 13th cent. or earlier; also cosdumna ; Occitan costuma ), Catalan †costuma (14th cent.), Italian costuma (1262), feminine (with the ending assimilated to the regular reflexes of Latin feminine nouns of the first declension). Compare also post-classical Latin coustuma , custuma customary payment, duty, toll (from 11th cent. in British (frequently) and continental sources), customary service or payment, or right to exact this (frequently from 11th cent. in British sources), (in plural) manners (11th cent.), accepted usage (14th cent. in a British source), and ( < French) Middle Dutch costūme , coustūme , custūme (Dutch †costume ), Middle Low German costūm , costūme , custūm , custūme , all in senses ‘convention, tradition’, ‘usage having the force of law’, and ‘(feudal or import or export) tax or duty’. Phonological development of the Latin etymon in Romance. It was formerly often suggested that the reflexes of classical Latin consuētūdin- , consuētūdō in the Romance languages immediately derive < an unattested post-classical Latin form *costumen (with suffix substitution after Latin nouns in -ūmen ). This view is now generally rejected, since precedents for such a morphological alteration are lacking. It is instead now generally held that the Romance forms reflect a series of phonological developments, probably successive assimilations and dissimilations, although the precise sequence of developments is unclear and may vary from one language to another. Specific senses. In by custom at sense A. 1c after Anglo-Norman par custume, Middle French par coutume (early 13th cent. or earlier); in of custom at sense A. 1c after Anglo-Norman de custume, Middle French de coutume (second half of the 13th cent. or earlier). In the custom of women at sense A. 1e ultimately after post-classical Latin consuetudo feminarum (Vulgate: Genesis 31:35; itself after Hebrew ḏereḵ nāšīm , lit. ‘the way of women’). In sense A. 2c after the corresponding specific use of Middle French, French coutume, †coustume (14th cent.; frequently in coutume de + the name of a town or region). In sense A. 3a the corresponding Old English term was toll toll n.¹ Later adjectival use (see sense B.) and uses in adverbial compounds (see Compounds 1c) are probably influenced by customer n.

Etymology: Partly (i) < Anglo-Norman custumer, coustumer, costumer (compare Middle French coutumer ) to pay customs duty (13th cent.), to make (a person) accustomed to something (second quarter of the 13th cent. or earlier), to become accustomed (to something) (end of the 14th cent. or earlier; < custume , coustume , costume custom n.), partly (ii, in later use) aphetic < accustom v., and partly (iii) < custom n. Compare post-classical Latin custumare to pay as customs (12th cent.), to assess for customs (frequently from 13th cent. in British sources), to pay customs on (1417 in a British source), to pay customs (15th cent. in a British source). With uses in sense 1 compare later accustom v.In Middle English prefixed and unprefixed forms of the past participle are attested (see y- prefix).