respectable adj.

1540s, "to regard, notice with especial attention," from French respecter "look back; respect; delay" (16c.), from Latin respectere, frequentative of respicere "look back at, regard, consider," from re- "back" (see re-) + specere "look at" (from PIE root *spek- "to observe").

The meaning "treat with deferential esteem, regard with some degree of reverence" is from 1550s. The sense of "refrain from injuring or interfering with" is from 1620s. The meaning "have reference to, relate to" is from 1560s. Related: Respected; respecting.

To respect the person was "show undue bias toward (or against) based on regard for the outward circumstances of a person;" hence respecter of persons, usually with negative, from Acts x:34, in the 1611 translation.

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.

1777, "state or character of being respectable; qualities which deserve or command respect," from respectable + -ity. By 1808 as "those who are respectable."