Sustain
Middle English: from Old French soustenir, from Latin sustinere, from sub- ‘from below’ + tenere ‘hold’.
wiktionary
From Middle English susteinen, sustenen, from Old French sustenir (French soutenir), from Latin sustineō, sustinēre(“to uphold”), from sub-(“from below, up”) + teneō(“hold”, verb).
etymonline
sustain (v.)
c. 1300, "give support to," from stem of Old French sostenir "hold up, bear; suffer, endure" (13c.), from Latin sustinere "hold up, hold upright; furnish with means of support; bear, undergo, endure," from assimilated form of sub "up from below" (see sub-) + tenere "to hold," from PIE root *ten- "to stretch." Meaning "continue, keep up" (an action, etc.) is from early 14c. Sense of "endure without failing or yielding" is from c. 1400. Related: Sustained; sustaining.
