It forms all or part of: ascertain; certain; concern; concert; crime; criminal; crisis; critic; criterion; decree; diacritic; discern; disconcert; discreet; discriminate; endocrine; excrement; excrete; garble; hypocrisy; incertitude; recrement; recriminate; riddle (n.2) "coarse sieve;" secret; secretary.
It is the hypothetical source of/evidence for its existence is provided by: Greek krinein "to separate, decide, judge," krinesthai "to explain;" Latin cribrum "sieve," crimen "judgment, crime," cernere "to sift, distinguish, separate;" Old Irish criathar, Old Welsh cruitr "sieve;" Middle Irish crich "border, boundary;" Old English hriddel "sieve."
mid-14c., regarden, "consider" (that something is so or a certain way), from Old French regarder "to look at, take notice of," from re-, here perhaps an intensive prefix, + garder "look, heed," from a Germanic language (see guard (n.)).
Sense of "consider of importance or interest" is from 1510s. Meaning "look upon, observe" is from 1520s, as is that of "observe a certain respect toward." From 1610s as "look upon" (with a certain feeling), "have or show a certain feeling for." Related: Regarded; regarding.