cropp

Old English cropp meant the head or top of a plant — the rounded, swollen upper part. It is from Proto-Germanic *kruppaz, meaning 'lump, round mass, body.' The same root produced 'group' (via French, from Italian groppo, 'knot'), 'croup' (the hindquarters of a horse), and 'croupier' (originally the person who sat behind a horseman). The semantic core is 'swollen rounded thing.' A crop was the swelling at the top of a stalk.

The bird meaning appeared early. A crop in a bird's anatomy is the expandable pouch in the esophagus where food is stored before digestion. The connection is the shape: a rounded swelling. Pigeons have prominent crops. Parrots have them. The anatomical term and the botanical term are the same word used for the same visual feature — a bulge at the top of a tube. The bird crop is likely the older meaning.

The agricultural meaning expanded by stages. The crop of a plant became the yield of the plant. The yield of one plant became the yield of a field. The yield of a field became the yield of a season. By the sixteenth century, 'the crop' meant the entire harvest — all the grain, all the fruit, everything the land produced that year. The word went from naming a part of a plant to naming the total output of agriculture. This is metonymy at its most extreme.

Modern usage has pushed even further. A crop of problems, a crop of graduates, a bumper crop of candidates. To crop a photograph means to cut its edges — from a different sense of 'crop' meaning to cut short (to crop hair, to crop ears). The cutting sense and the growing sense are the same word with opposite implications: one adds, the other removes. English did not notice the contradiction. It rarely does.