What is "custom of merchants"

Custom \Cus"tom\ (k[u^]s"t[u^]m), n. [OF. custume, costume, Anglo-Norman coustome, F. coutume, fr. (assumed) LL. consuetumen custom, habit, fr. L. consuetudo, -dinis, fr. consuescere to accustom, verb inchoative fr. consuere to be accustomed; con- + suere to be accustomed, prob. originally, to make one's own, fr. the root of suus one's own; akin to E. so, adv. Cf. Consuetude, Costume.]

1. Frequent repetition of the same act; way of acting common to many; ordinary manner; habitual practice; usage; method of doing or living.

   And teach customs which are not lawful.
   --Acts xvi. 21.

   Moved beyond his custom, Gama said.
   --Tennyson.

   A custom More honored in the breach than the observance.
   --Shak.

2. Habitual buying of goods; practice of frequenting, as a shop, manufactory, etc., for making purchases or giving orders; business support.

   Let him have your custom, but not your votes.
   --Addison.

3. (Law) Long-established practice, considered as unwritten law, and resting for authority on long consent; usage. See Usage, and Prescription.

   Note: Usage is a fact. Custom is a law. There can be no custom without usage, though there may be usage without custom.
   --Wharton.

4. Familiar aquaintance; familiarity. [Obs.]

   Age can not wither her, nor custom stale Her infinite variety.
   --Shak.

   Custom of merchants, a system or code of customs by which affairs of commerce are regulated.

   General customs, those which extend over a state or kingdom.

   Particular customs, those which are limited to a city or district; as, the customs of London.

   Syn: Practice; fashion. See Habit, and Usage.