gen. A person who acts for another; an agent, deputy, or representative. Now chiefly historical.

gen. A person who or thing which provides assistance, or constitutes the means by which assistance may be obtained; an aid; an accessory. Obsolete.

(under-, prefix1 affix 3a(b).)

A subsidiary or subordinate thing; something which provides additional support or assistance; an auxiliary, an aid.

(under-, prefix1 affix 3a(b).)

transferred and figurative (cf. contribution, n. 3a.)

transferred and figurative. One who or that which furnishes subsidiary supplies or aid. Of other things.

One who or that which contributes; a contributing factor or person.