Definition of mattie:
(n) :
A diminutive of the female given name Matilda, also used as a formal given name
(n) :
A diminutive of the female given name Martha, also used as a formal given name
(n) :
A diminutive of the female given name Madeline, variant of Maddie
(n) :
Alternative form of matie (“herring”). [(UK and Scotland, archaic) A fat herring with undeveloped roe.]