Swollen means puffed up bigger than it should be. An ankle after a fall, a river after a week of rain.
It is the past participle of swell used as an adjective, and it usually signals injury, infection or excess water. Doctors use it constantly, and swollen glands and a swollen joint are standard. Rivers swell too, and a swollen river is one about to break its banks. There is a figurative use for numbers, since swollen ranks means a group that has grown, and swollen-headed means conceited.
1adjectiveswollenEnlarged beyond the normal size, usually by injury or fluid.
“His knee was badly swollen by the morning.”
Proto-Germanic
*swullanaz
Old English
swollen
Middle English
swollen
English, today
swollen
From Middle English swollen, i-swolle, y-swolle, yswolle, ȝeswollen, from Old English swollen, ġeswollen, from Proto-Germanic swullanaz, past participle of Proto-Germanic swellaną (“to swell”). Cognate with West Frisian swollen (“swollen”), Dutch gezwollen (“swollen”), German geschwollen (“swollen”), Swedish svullen (“swollen”).
Etymology from Wiktionary, CC BY-SA