passable adj.

late 13c., passen (transitive), "to go by (something)," also "to cross over," from Old French passer "to pass" (11c.), from Vulgar Latin *passare "to step, walk, pass" (source also of Spanish pasar, Italian passare), from Latin passus "step, pace" (from PIE root *pete- "to spread").

Intransitive sense of "to go on, to move forward, make one's way" is attested from c. 1300. The figurative sense of "to experience, undergo" (as in pass the time) is recorded from late 14c. Sense of "to go through an examination successfully" is from early 15c. Meaning "decline to do something" is attested from 1869, originally in cards (euchre). In football, hockey, soccer, etc., the meaning "to transfer the ball or puck to another player" is from c. 1865. Related: Passed; passing.

The meaning "to be thought to be something one is not" (especially in a racial sense) is from 1935, from pass oneself off(as), which is attested by 1809. The general verb sense of "to be accepted as equivalent" is from 1590s. Pass up "decline, refuse" is attested from 1896. Pass the buck is from 1865, said to be poker slang reference to the buck horn-handled knife that was passed around to signify whose turn it was to deal. Pass the hat "seek contributions" is from 1762. Pass-fail as a grading method is attested from 1955, American English.

common termination and word-forming element of English adjectives (typically based on verbs) and generally adding a notion of "capable of; allowed; worthy of; requiring; to be ______ed," sometimes "full of, causing," from French -able and directly from Latin -abilis. It is properly -ble, from Latin -bilis (the vowel being generally from the stem ending of the verb being suffixed), and it represents PIE *-tro-, a suffix used to form nouns of instrument, cognate with the second syllables of English rudder and saddle (n.).

A living element in English, used in new formations from either Latin or native words (readable, bearable) and also with nouns (objectionable, peaceable). Sometimes with an active signification (suitable, capable), sometimes of neutral signification (durable, conformable). It has become very elastic in meaning, as in a reliable witness, a playable foul ball, perishable goods. A 17c. writer has cadaverable "mortal."

To take a single example in detail, no-one but a competent philologist can tell whether reasonable comes from the verb or the noun reason, nor whether its original sense was that can be reasoned out, or that can reason, or that can be reasoned with, or that has reason, or that listens to reason, or that is consistent with reason; the ordinary man knows only that it can now mean any of these, & justifiably bases on these & similar facts a generous view of the termination's capabilities; credible meaning for him worthy of credence, why should not reliable & dependable mean worthy of reliance & dependence? [Fowler]

In Latin, -abilis and -ibilis depended on the inflectional vowel of the verb. Hence the variant form -ible in Old French, Spanish, English. In English, -able tends to be used with native (and other non-Latin) words, -ible with words of obvious Latin origin (but there are exceptions). The Latin suffix is not etymologically connected with able, but it long has been popularly associated with it, and this probably has contributed to its vigor as a living suffix.

"that cannot be passed or passed over," 1560s, from assimilated form of in- (1) "not, opposite of" + passable. Related: Impassability.