the.com/buttonhole

means As a noun, the small slit a button passes through to fasten clothing; as a verb, to grab someone's attention and detain them in conversation, often against their will.

from The noun is old tailoring vocabulary, straightforward as cloth and thread. The verb's story is the fun part: it grew out of 'button-hold,' the literal act of physically grabbing a man's coat button (or buttonhole) to stop him walking off while you finished talking at him. Over time 'hold' slurred into 'hole,' and the physical grab faded into the purely verbal kind — you don't need to touch someone's coat to buttonhole them at a party, but the ghost of that grasping hand is still in the word.