[thin, few, unusual] late 14c., "thin, airy, porous" (opposed to dense); mid-15c., "few in number and widely separated, sparsely distributed, seldom found, very infrequent;" from Old French rer, rere "sparse" (14c.) and directly from Latin rarus "thinly sown, having a loose texture; not thick; having intervals between, full of empty spaces" (antonym of densus). Sometimes reconstructed to be from a PIE root *ere- "to separate; adjoin."
"Having the particles not close together," hence "few in number," hence, "unusual." Sense of "remarkable from uncommonness," especially "uncommonly good" is from late 15c. (Caxton). Related: Rareness. In chemistry, rare earth is from 1818.
Rare implies that only few of the kind exist : as, perfect diamonds are rare. Scarce properly implies a previous or usual condition of greater abundance. Rare means that there are much fewer of a kind to be found than may be found where scarce would apply. [Century Dictionary, 1895]
1680s, "large tent of unusual elaborateness," from French marquise (mistaken in English as a plural) "linen canopy placed over an officer's tent to distinguish it from others,' " fem. of marquis (see marquis), and perhaps indicating "a place suitable for a marquis."
By 1812 the English word was used of large wooden structures erected for a temporary purpose (a concert, dinner party, etc.). The extended sense of "canopy over the entrance to a hotel or theater, etc." is recorded by 1912 in American English.
late 15c., "to go through searchingly or in detail, run over with careful scrutiny," from Middle English per- "completely" (see per) + use (v.). Meaning "read carefully and critically" is by 1530s, but this could be a separate formation. Meaning "read casually" is from 19c. Related: Perused; perusing. "The formation looks unusual, but it is well supported by similar formations now obsolete, e.g. peract, perplant, perstand, etc." [Century Dictionary].