Convertible

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late Middle English (in the sense ‘interchangeable’): from Old French, from Latin convertibilis, from convertere ‘turn about’ (see convert).

wiktionary

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From Old French convertible, from Late Latin convertibilis(“ interchangeable”), from Latin convertere(“to turn back, to turn over, to turn around, to turn upside down”), from con-(“ with, together”) + vertere(“to turn”), + -ibilis(“ -ible: able to”). Equivalent to convert +‎ -ible.

etymonline

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convertible (adj.)

late 14c., "interchangeable," from Old French convertible "interchangeable" (13c.) and directly from Late Latin convertibilis "changeable," from Latin convertere "to turn around; transform," from assimilated form of com "with, together" (see con-) + vertere "to turn" (from PIE root *wer- (2) "to turn, bend").

Meaning "capable of being changed in form, substance, or condition" is from 1530s. Of paper money, etc., "capable of being converted into gold of a similar amount," from 1834. The noun is recorded from 1610s; meaning "automobile with a fold-down top" is from 1916. Related: Convertibility.