"that which is lacking in sense, language or words without meaning or conveying absurd or ridiculous ideas," 1610s, from non- "not" + sense (n.); perhaps influenced by French nonsens. Since mid-20c., non-sense, with the hyphen, has been used to distinguish the meaning "that which is not sense, that which is different from sense," not implying absurdity.
1570s, from French sentinelle (16c.), from Italian sentinella "a sentinel." OED says "No convincing etymology of the It. word has been proposed," but perhaps (via a notion of "perceive, watch"), from sentire "to hear," from Latin sentire "feel, perceive by the senses" (see sense (n.)).
"a direct, though vague, perception of a future event," 1714, from French presentiment (Modern French pressentiment), from pressentir "to have foreboding," from Latin praesentire "to sense or feel beforehand," from prae "before" (see pre-) + sentire "perceive, feel" (see sense (n.)). Especially a feeling that some misfortune or calamity is about to happen, a foreboding.
early 14c., dissencioun, "disagreement in opinion," especially strong disagreement which produces heated debate, from Old French dissension (12c.) and directly from Latin dissensionem (nominative dissensio) "disagreement, difference of opinion, discord, strife," noun of action from past participle stem of dissentire "disagree," from dis- "differently" (see dis-) + sentire "to feel, think" (see sense (n.)).
1854, "a general accord or agreement of different parts in effecting a given purpose," originally a term in physiology; 1861, of persons "a general agreement in opinion;" from Latin consensus "agreement, accord," past participle of consentire "feel together," from assimilated form of com "with, together" (see con-) + sentire "to feel" (see sense (n.)). There is an isolated instance of the word from 1633.
c. 1300, "agree, give assent; yield when one has the right, power, or will to oppose," from Old French consentir "agree; comply" (12c.) and directly from Latin consentire "agree, accord," literally "feel together," from assimilated form of com "with, together" (see con-) + sentire "to feel" (see sense (n.)).
"Feeling together," hence, "agreeing, giving permission," a sense evolution that apparently took place in French before the word reached English. Related: Consented; consenting.