The only free and comprehensive online etymological dictionary of the Spanish language
regresión f. (Noun) "regression"
16th cent. From Latin regressionem, accusative of regressio 'id.' Formed from regressus "return" (see regreso).
regreso m. (Noun) "return"
16th cent. From Latin regressus 'id.,' from regredi "to return," from re- and gredi "to walk" (see agredir).
regular (1) (Verb) "to measure," "to determine"
17th cent. From Late Latin regulare 'id.,' from Latin regula "rod," "rule" (see regla).
Indo-European
Romance
Asturian regular, Portuguese regular, Catalan regular, French réguler, Italian regolare, Romanian regula
regular (2) (Adjective) "regular"
Late 15th cent. From Latin regularis 'id.,' from Latin regula "rod," "rule" (see regla).
Indo-European
Romance
Asturian regular, Portuguese regular, Catalan regular, French régulier, Italian regolare, Romanian regular
reina f. (Noun) "queen"
12th cent. Originally pronounced reína, the stress was regularized in sometime in the 15th cent. From Latin regina 'id.' From Proto-Italic *reg-īna- 'id.,' formed from the adjective *reg-īno- "regal." From *rēg- "king" (see rey).
The surnames Reina, Reyna, and Reine refer to the moniker of Mary, Regina Cœli "queen of heaven," found in ancient Christian hyms.
Indo-European
Romance
Asturian reina, Portuguese rainha, Galician raíña, Catalan reina, French reine, Italian regina, Romanian regină, Sardinian reina
Italic
Marsian regen "queen"
reino m. (Noun) "kingdom;" "reign"
12th cent. From Latin regnum 'id.' From Proto-Italic *rēg- "king" (see rey).
Indo-European
Romance
Asturian reinu, Portuguese reino, Galician reino, Catalan regne, French règne, Italian regno, Sardinian regnu, arregnu
reír (Verb) "to laugh"
13th cent. From Latin redire 'id.' Of unknown origin.
Indo-European
Romance
Asturian rir, Portuguese rir, Galician rir, Catalan riure, French rire, Italian ridere, Aromanian arãd, Romanian râde, Sardinian ridere
reja (1) f. (Noun) "plowshare"
13th cent., earlier 10th cent. Old Spanish rella. From Latin regula "bar," but also meaning "rule." From regere "to govern" (see regir) and the instrumental suffix -ula.
reja (2) f. (Noun) "grating"
15th cent. Borrowed from Catalan reixa 'id.,' from Vulgar Latin *regla 'id.,' from Latin regula "bar." From regere "to govern" (see regir) and the instrumental suffix -ula.
relación f. (Noun) "relation;" "relationship"
From Latin relationem, accusative of relatio 'id.' From referre "to carry back," from re- "again" (see re-) and ferre "to bring" (see -fero).
Indo-European
Romance
Portuguese relação, French relation, Italian relazione, Romanian relație