customer

Etymology

From Middle English customere, custommere, from Old French coustumier, costumier (compare modern French coutumier), from Medieval Latin custumarius (“a toll-gatherer, tax-collector”, noun), from custumarius (“pertaining to custom or customs”, adjective), from custuma (“custom, tax”). More at custom. By surface analysis, custom + -er.

noun

1. (obsolete) A habitual patron, regular purchaser, returning client; one who has a custom of buying from a particular business.
2. A patron, a client; one who purchases or receives a product or service from a business or merchant, or intends to do so.
   Every person who passes by is a potential customer.
3. (informal) A person, especially one engaging in some sort of interaction with others.
   a cool customer, a tough customer, an ugly customer
   Pug could just see Slote's pale face under his fur hat. "I don't agree with you on that. He's a pretty tough customer, Hopkins." 1971, Herman Wouk, chapter 52, in The Winds of War]
   This switch led to Philip Hammond becoming the Transport Secretary and he quickly proved to be a tricky customer, asking questions about rail spending and reining it back whenever possible. January 2 2020, Philip Haigh, “Ten eventful years and plenty of talking points”, in Rail, page 54
4. (India, historical) A native official who exacted customs duties.
   His houses […] are seized on by the Customer. 1609, Danvers, Letters, i. 25; and comp. Foster, ibid. ii. 225
   The Customer should come and visit them. 1615, Sir T. Roe, Hak. Soc. i. 44
   The several affronts, insolences, and abuses dayly put upon us by Boolchund, our chief Customer 1682, Hedges, Diary [Hak. Soc. i. 33]