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

17th cent. Borrowed from Latin manducare 'id.' From mandere "to chew." From Proto-Italic *mand-n- "to chew" but originally "to stir." From Proto-Indo-European *menth2- 'id.'

Romance: Western Vulgar Latin: Portuguese manjar, Catalan menjar, French manger, Italian manducare; Eastern Vulgar Latin: Aromanian mãc, Romanian mânca; Sardinian: mandhicare

Indo-European: Balto-Slavic: Old Church Slavonic męsti "to disturb," Russian mjastí 'id.,' Czech másti "to confuse," Slovene mę́sti "to disturb," Lithuanian mę̃sti "to mix;" Indo-Iranian: Sanskrit mánthanti "they whirl," Ossetic yzmæntyn "to stir"
manejar (Verb) (Latin America) "to drive;" "to manage"

Late 16th cent. Borrowed from Italian maneggiare 'id.' From Vulgar Latin *manidiare "to manage," a verbal derivative of manus "hand" (see mano).
manera f. (Noun) "manner"

12th cent. From Latin manuaria "skillful," composed of manus "hand" and -aria, a noun-forming suffix indicating a user or agent. See mano and -ero respectively for further etymologies.

Romance: Western Vulgar Latin: Portuguese maneiro, Italian mannaia; Eastern Vulgar Latin: Aromanian mãnar, Romanian mâner
mano f. (Noun) "hand"

10th cent. From Latin manus 'id.' From Proto-Italic *man-u- 'id.' From Proto-Indo-European *m̥h2-no- 'id.' From a root *meh2- of uncertain value, but likely connected to waving or summoning.

Romance: Western Vulgar Latin: Asturian mano, Portuguese mão, Galician man, Catalan , French main, Italian mano; Eastern Vulgar Latin: Aromanian mãnã, Romanian mână; Sardinian: manu

Italic: Oscan manim "hand," Umbrian manuve "on the hand," South Picene manus "by the hand"

Indo-European: Celtic: Old Irish muin "protection," Middle Welsh mynawc "prince;" Germanic: Old Norse mund "hand," Old High German munt "hand," "protection," Old English mund 'id.;' Hellenic: Ancient Greek μάρη (máre) "hand;" Anatolian: Hittite manii̯aḫḫ-i "to distribute," "to hand over"
mantener (Verb) "to maintain"

Borrowed from Medieval Latin manutenere 'id.,' literally "to hold by hand." From manus "hand" (see mano) and tenere "to hold" (see tener).

Romance: Western Vulgar Latin: Asturian mantener, Portuguese manter, Galician manter, French maintenir, Italian mantenere
manzana (1) f. (Noun) "apple"

12th cent. Old Spanish mazana. From Vulgar Latin mattiana 'id.' From Latin mala Mattiana, a golden apple varietal but lit. "Matian apples." Named after the horticulturist Gaius Matius, friend of Cæsar Agustus, who introduced the technique of clipping trees. Mala "apples" (singular malum) was borrowed from Ancient Greek μῆλον ‎(mêlon) "fruit," "tree." Of unknown origin.

Also the origin of the surnames Manzanas and Mansana.
manzana (2), manzana de Adán f. (Noun) (Latin America) "Adam's apple"

From Latin pomum Adami "Adam's apple," a mistranslation of Hebrew tappuach ha-adam "man's bump" for "Adam's apple."

Romance: French pomme d'Adam (English Adam's apple, a calque of the French)
manzanilla f. (Noun) "manzanilla"

10th cent. Old Spanish massanella, late 15th cent. manzanilla. Literally "little apple" (see manzana (1)). So-called for its visual similarity with an apple and its flower bud.
mapa m. (Noun) "map"

16th cent. Borrowed from Medieval Latin mappa 'id.' From Latin mappa "napkin," "tablecloth." Of unknown origin, thought to be from a Semitic language (cf. Hebrew mapá "map," "tablecloth").

Romance: Western Vulgar Latin: Portuguese mapa, Italian mappa
máquina f. (Noun) "machine"

15th cent. Borrowed from Latin machina 'id.,' itself borrowed from Ancient Greek μαχανά ‎(makhaná) "machine," "tool." Of unknown origin. Presumably borrowed from another language.

Romance: Western Vulgar Latin: Portuguese máquina, Galician máquina, Catalan màquina, French machine, Italian macchina; Eastern Vulgar Latin: Romanian mașină