case ending

noun Grammar.

a suffix on an inflected noun, pronoun, or adjective that indicates its grammatical function.

Origin of case ending

First recorded in 1870–75

Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Thus, portam (Accusative Singular) is formed by adding the case-ending -m to the stem porta-.
New Latin Grammar
Charles E. Bennett