Here are some common linguistics abbreviations; thanks, jheem.

IE Indo-European (as in the IE lgs)
PIE Proto-Indo-European (as in the hypothetical ancestor of the IE lgs)
OE Old English
ME Middle English
NE / PDE Modern English (New English and Present Day English)
OFr, MFr, Fr Old, Middle, and Modern French
Gk Greek
Skt Sanskrit
L Latin
adj adjective
sb substantive / noun
adv adverb
vb verb