commonplace n.

c. 1300, "belonging to all, owned or used jointly, general, of a public nature or character," from Old French comun "common, general, free, open, public" (9c., Modern French commun), from Latin communis "in common, public, shared by all or many; general, not specific; familiar, not pretentious." This is from a reconstructed PIE compound *ko-moin-i- "held in common," compound adjective formed from *ko- "together" + *moi-n-, suffixed form of root *mei- (1) "to change, go, move," hence literally "shared by all."

The second element of the compound also is the source of Latin munia "duties, public duties, functions," those related to munia "office." Perhaps reinforced in Old French by the Germanic form of PIE *ko-moin-i- (compare German gemein, Old English gemne "common, public, general, universal;" see mean (adj.)), which came to French via Frankish.

Used disparagingly of women and criminals since c. 1300. Meaning "pertaining equally to or proceeding equally from two or more" is from c. 1400. Meaning "usual, not exceptional, of frequent occurrence" is from late 14c. Sense of "not distinguished, belonging to the general mass" is from c. 1400; of things, "ordinary, not excellent," late 14c.

Common pleas is 13c., from Anglo-French communs plets, hearing civil actions by one subject against another as opposed to pleas of the crown. Common prayer is that done in public in unity with other worshipers; contrasted with private prayer. Common stock is attested from 1888. Common speech (late 14c.) is the vernacular, as opposed to Latin. Common good (late 14c.) translates Latin bonum publicum "the common weal." The college common room (1660s) is one to which all members have common access. 

c. 1200, "space, dimensional extent, room, area," from Old French place "place, spot" (12c.) and directly from Medieval Latin placea "place, spot," from Latin platea "courtyard, open space; broad way, avenue," from Greek plateia (hodos) "broad (way)," fem. of platys "broad," from PIE root *plat- "to spread."

Replaced Old English stow and stede. From mid-13c. as "particular part of space, extent, definite location, spot, site;" from early 14c. as "position or place occupied by custom, etc.; precedence, priority in rank or dignity; social status, position on some social scale;" from late 14c. as "inhabited place, town, country," also "place on the surface of something, portion of something, part." Meaning "a situation, appointment, or employment" is by 1550s. Meaning "group of houses in a town" is from 1580s.

Also from the same Latin source are Italian piazza, Catalan plassa, Spanish plaza, Middle Dutch plaetse, Dutch plaats, German Platz, Danish plads, Norwegian plass. The word appears via the Bible in Old English (Old Northumbrian plaece, plaetse "an open place in a city"), but the modern word is a reborrowing.

Sense of "a mansion with its adjoining grounds" is from mid-14c.; that of "building or part of a building set apart for some purpose is by late 15c. (in place of worship). Meaning "a broad way, square, or open space in a city or town," often having some particular use or character (Park Place, Waverly Place,Rillington Place) is by 1690s, from a sense in French. Its wide application in English covers meanings that in French require three words: place, lieu, and endroit. Cognate Italian piazza and Spanish plaza retain more of the etymological sense.

To take place "happen, come to pass, be accomplished" (mid-15c., earlier have place, late 14c.), translates French avoir lieu. To know (one's) place "know how to behave in a manner befitting one's rank, situation, etc." is from c. 1600, from the "social status" sense; hence the figurative expression put (someone) in his or her place (1855). In in the first place, etc., it has the sense of "point or degree in order of proceeding" (1630s). Out of place "not properly adjusted or placed in relation to other things" is by 1520s. All over the place "in disorder" is attested from 1923.