custom (n.) Look up custom at Dictionary.com
c.1200, "habitual practice," from Old French costume "custom, habit, practice; clothes, dress" (12c., Modern French coutume), from Vulgar Latin *consuetumen, from Latin consuetudinem (nominative consuetudo) "habit, usage, way, practice, tradition, familiarity," from consuetus, past participle of consuescere "accustom," from com-, intensive prefix (see com-), + suescere "become used to, accustom oneself," related to sui, genitive of suus "oneself," from PIE *swe- "oneself" (see idiom). Replaced Old English þeaw. Sense of a "regular" toll or tax on goods is early 14c. The native word here is toll.
custom (adj.) Look up custom at Dictionary.com
"made to measure or order," c.1830, from custom (n.).