The only free and comprehensive online etymological dictionary of the Spanish language
calmar (Verb) "to calm"

15th cent. From calma.
calor m. (Noun) "heat"

13th cent. From Latin calor 'id.' Derived from calere "to be hot." See caliente for a continued etymology.

Romance: Western Vulgar Latin: Asturian calor, Portuguese calor, Galician calor, Catalan calor, French chaleur, Italian calore; Eastern Vulgar Latin: Aromanian cãroari; Sardinian: calore
cama f. (Noun) "bed"

13th cent. From a pre-Roman language, usually assumed to be Iberian but ultimately unknown.

Also the origin of the surname Cama, first given to bed-makers and sellers.

Romance: Western Vulgar Latin: Asturian cama, Leonese cama, Portuguese cama, Galician cama

The word originally indicated a straw bed while lecho was the generic term for bed. Cama eventually replaced lecho in the medieval period.
cámara (1) f. (Noun) "camera"

A shortening of the name camera obscura, Latin for "dark room," a lightbox re-introduced to the West from the Arab world during the Renaissance. For the etymology of camera and obscura, see cámara (2) and oscuro respectively.
cámara (2) f. (Noun) "chamber"

12th cent. Borrowed from Latin camera 'id.,' borrowed from Ancient Greek καμάρα ‎(kamára) 'id.' Of unknown origin. Probably borrowed from an Asiatic language.

Also the origin of the surnames Cámara, de la Cámara, and Lacámara. Originally given to heads of households endowed with direct, personal access to the king.
cambiar (Verb) "to change"

11th cent. From Late Latin cambiare, from Latin cambire "to exchange." From Gaulish cambion "change." Of unknown origin. Possibly from a substrate source.

Romance: Western Vulgar Latin: Aragonese cambear, Asturian cambiar, Portuguese cambiar, Galician cambiar, Catalan canviar, French changer, Italian cambiare; Eastern Vulgar Latin: Romanian schimba (excambiare; compare English change ~ exchange); Sardinian: cambiare

Celtic: Continental *kambo-: Gaulish Cambo "crooked;" Goidelic *kambo-: Old Irish camm 'id.;' Brythonic *kambo-: Old Welsh cam "evil," Old Breton camm "slanting," Cornish cam

Hellenic: Ancient Greek σκαμβός (skambós) "crooked," σκιμβός (skimbós) "crooked," "lame"

The original word was camear but was replaced in the Middle Ages by cambiar, which the learned class took to be closer to the Latin. The scholastics sometimes replaced native words with new ones that they believed were closer to the older Latin (for example, ambos which replaced amos).
cambio m. (Noun) "change;" (money) "change"

11th cent. From cambiar.

Romance: Western Vulgar Latin: Asturian cambéu "change," cambiáu (money) "change" (cambear) Galician cambio, Catalan canvi, Italian cambio
caminar (Verb) "to walk"

13th cent. From camino.

Romance: Western Vulgar Latin: Asturian caminar, Galician camiñar, Catalan caminar, Italian camminare
camino m. (Noun) "way," "road"

11th cent. From Latin camminus, borrowed from the Gaulish language. From Proto-Celtic *kanxsman "step." Compare Old Welsh cemmein "step." From *keng-o- "to step." From Proto-Indo-European *(s)keng- "to walk."

Also the origin of the surnames Camino, del Camino, and Caminos, given to men and families who owned houses situated along rural roads, distant from other houses.

Romance: Western Vulgar Latin: Asturian camín, Portuguese caminho, Galician camiño, Catalan camí, French chemin, Italian cammino

Celtic: Goidelic: Old Irish céimm; Brythonic: Old Welsh cemmein, Middle Breton cam, Cornish cam
camión m. (Noun) "truck"

19th cent. Borrowed from French camion 'id.' Old French chamion. Of unknown origin. Probably related to a borrowed non-Indo-European root *kam- "way," "path" (compare Celtiberian kamanom "way;" Vulgar Latin *camminus "way" (see camino)).