late 14c., "careful observation of one's surroundings, attention to details and probable consequences" (with a view to choosing the safest course), from Old French circumspection (Modern French circonspection), from Latin circumspectionem (nominative circumspectio) "a looking around; foresight, caution," noun of action from past participle stem of circumspicere "to look around," from circum "around, round about" (see circum-) + specere "to look" (from PIE root *spek- "to observe"). 

mid-14c., "a consideration; a judgment," from Old French regard, regart, from regarder "take notice of," from re-, here perhaps an intensive prefix, + garder "look, heed," from a Germanic language (see guard (n.)).

Meanings "a look, appearance; respect, esteem, favor, kindly feeling which springs from a consideration of estimable qualities" all are recorded late 14c. Phrase in regard to is from mid-15c. (Chaucer uses at regard of).

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.