Douglas Harper's Etymology Dictionary
"add strength," 1941, from college slang, from beef (n.) in slang sense of "muscle-power" (1851).
Wiktionary
vb. (context idiomatic English) to strengthen or reinforce; to add substance to
WordNet
v. make strong or stronger; "This exercise will strengthen your upper body"; "strenghten the relations between the two countries" [syn: strengthen, fortify] [ant: weaken]
Usage examples of "beef up".
Jonathan thought that the two on the fishing trawler were probably drinking their pint at the old Mooneye right at that moment and that old Monroe was likely shoving a joint of beef up onto a spit while his wife cleaned potatoes and rolled out crusts for pies.
But I've been driving my own beef up to Corpus Christi on the hoof.
Mills seemed to be sizing Beef up, deciding whether to be frank or not.
In accordance with the new directive, the army announced that it would beef up the Two-Two-Two by adding 1,500 volunteers from Hawaii and 1,500 from the mainland, but the plan didn't work because in Honolulu 11,800 rushed forward to serve, stampeding the registration booths.
We'll hit every caravan we can, force the Slavers' Guild to beef up their caravans, adding more and more guards, cutting down on the profits from slaving.
Figuring all our herds consolidated, we got near fifty thousand dollars worth of beef up in our valley!
Bad enough so the USA couldn't say no when we asked to beef up the Army a bit—.
People we can send anywhere, very quietly, to beef up native forces, so that it won't be necessary to send out regiments and divisions.