The word 'supportable' is a late Middle English formation built upon the verb 'support', which entered English via Old French from the Latin supportare. This Latin verb itself is a compound of sub-, meaning 'up from below', and portare, meaning 'to carry', painting a literal picture of bearing a weight from beneath. The suffix -able, of Latin origin via French, was attached to create an adjective meaning 'capable of being carried or borne'. Over time, the physical sense of bearing a load evolved metaphorically, leading to the modern abstract meanings of being tolerable (able to be endured) or defensible (able to be upheld).

Structure: support + able - support: From Latin supportare ('to carry, bring up, convey'), from sub- ('up from under') + portare ('to carry'). Functions as the verb root. - able: From Latin -abilis ('able to be, capable of'), an adjective-forming suffix indicating capacity or susceptibility.