To close up is to shut for the day, or to heal over. Close up the shop, the wound closed up, closing up for the night.
The healing sense is the older, and a wound left to close up over an infection is a real problem. Written with a hyphen it becomes a noun meaning a photograph taken very near.
1phraseclose upTo shut for the day, or to heal over.
“The café owners close up at six and head home.”
close up is a shutting.
A rearranged form of Middle English upclosen, to close up or seal.
Middle English
upclosen — to close up, stop up, seal
English, today
close up
Dissimilated from Middle English upclosen (“to close up, stop up, seal”).
Etymology from Wiktionary, CC BY-SA
Practised in Phrasal Verbs