The only free and comprehensive online etymological dictionary of the Spanish language
rato (1) m. (Noun) "brief time;" "moment"

13th cent. From Latin raptus "carried (away)." From rapere "to seize" (see raptar).

Romance: Western Vulgar Latin: French rapt
rato (2) (Adjective) "confirmed"

From Latin ratus "established." From Proto-Italic *rato- "thought." From Proto-Indo-European *Hr̥h1-to- "counted."

Indo-European: Germanic: Gothic raþjo "number," Old High German redea "account," Old Saxon rethia 'id.'
rayo m. (Noun) "ray"

13th cent. From Latin radius 'id.' Of unknown origin.

Romance: Western Vulgar Latin: Portuguese raio, Catalan raig, French rai, Italian raggio ; Eastern Vulgar Latin: Aromanian radzã, Romanian rază ; Sardinian: ragiu
razón f. (Noun) "reason;" "correctness"

12th cent. Vulgar Latin ratione. Unexpected voicing from [ts] in Vulgar Latin into [dz] in Old Spanish must have ocurred very anciently: by the 12th cent., the word is already written razón instead of the expected raçón. From Latin rationem, accusative of ratio 'id.,' from ratus "established," the passive participle of reri "to consider." See rata for further etymology.

Romance: Western Vulgar Latin: Asturian razón, Portuguese razão, Galician razón, Catalan raó, French raison, Italian razione ; Eastern Vulgar Latin: Romanian rațiune ; Sardinian: rajone
re- Prefix indicating "again" or "back"

From Latin re(d)- 'id.' From Proto-Italic *wre- 'id.' From Proto-Indo-European *u̯re- 'id.'

Italic: Umbrian re- "again"

Indo-European: Balto-Slavic *u̯re-h3kwo- "looking backward": Russian rak "crayfish," Czech rak 'id.,' Polish rak 'id.,' Slovene ràk 'id.,' Lithuanian érkė "tick," Latvian ẽrce 'id.;' Albanian: rrë- "back"
real (Adjective) "real"

16th cent. From Latin realis "actual," from res "thing" and -alis, an adjective-forming suffix indicating a relationship (see -al (2)).

Romance: Western Vulgar Latin: Portuguese real, French réel, Italian reale ; Eastern Vulgar Latin: Romanian real
realidad f. (Noun) "reality"

16th cent. From Medieval Latin realitatem, accusative of realitas 'id.' From realis "real" (see real) and -tas, noun-forming suffix (see -dad).

Romance: Western Vulgar Latin: Portuguese realidade, Catalan realitat, French réalité, Italian realtà ; Eastern Vulgar Latin: Romanian realitate
realmente (Adverb) "actually"

From real and -mente.
recibir (Verb) "to receive"

Very early 12th cent. From Latin recipere 'id.' From re- "again" (see re-) and capere "to take" (see caber).
recibo m. (Noun) "receipt;" "reception"

Very early 17th cent. From recibir.