The only free and comprehensive online etymological dictionary of the Spanish language
tumba (2) f. (Noun) "tumble"

18th cent. From tumbar.
tumbar (Verb) "to tumble"

18th cent. From Vulgar Latin *tumbare 'id.' Of unknown origin but probably of onomatopoeic origin.
turnar (Verb) "to take turns"

18th cent. Borrowed from French tourner 'id.,' from Latin tornare "to turn (in a lathe)." From Latin tornus "lathe" (see torno).

Romance: Western Vulgar Latin: Asturian tornar Portuguese tornar, Galician tornar, Catalan tornar, French tourner, Italian tornare ; Eastern Vulgar Latin: Aromanian tornu, Romanian turna ; Sardinian: torràe
turno m. (Noun) "turn"

17th cent. However it appears in a single documented name from early 13th cent., Felicia del Malturno. From turnar.
tuyo (Possessive Pronoun) "(of) yours"

From Latin tuus 'id.' From tu "you" interpreted as a noun (see ).