Note:
(a)
(i) magus (n; Latin, from Greek magos — more at MAGIC):
"1b often capitalized : one of the traditionally three wise men from the East paying homage to the infant Jesus
2: MAGICIAN, SORCERER" http://www.merriam-webster.com/dictionary/magus
(ii) Because "magus" is Latin, its plural form is "magi." Note the change of pronunciation--in ENGLISH (but not so in Latin)--in "g" between singular and plural forms (I introduce the pronunciation in Collins English Dictionary, because m-w.com does not provide one for the plural form.) http://www.collinsdictionary.com/dictionary/english/magi
(ii) puella. Wikitionary. http://en.wiktionary.org/wiki/puella
(Latin, singular form: "a girl"; etymology: from puellus (“a little boy”), contracted from puerulus (“a little boy, a little slave”) the diminutive of puer (“boy”))
(A) Both "puellus" and "puer" are Latin nouns.
(B) Thast is why English adjective puerile means "childish."