Bespoke is an adjective for anything commissioned to a particular specification. “Custom-made”, “made to order”, “made to measure” and sometimes “hand-made” are near-synonyms, and “off-the-shelf”, and in clothing ready-to-wear, are the opposite. Modding is a slang term, mostly used for personalization after manufacture.
The word bespoke is derived from the verb to bespeak, to “speak for something”, in the specialised meaning “to give order for it to be made” or commission, first cited from 1583 by the OED, with the adjective in its alternative form “bespoken” first quoted from 1607 in this sense. The term is generally more prevalent in British English than American English, which tends to use “custom” instead, as in custom car, custom motorcycle etc.
I think I will be adding this to all my blogs, websites, and personal information pages