vessels, counter for ships, fish, birds, arrows, one of a pair
JLPT2 G7 S10 F1546
An abbreviated form of 雙 (pair of birds), removing one of the 隹 bird elements in order to indicate *one of a pair* → *sole*; *only*; *a few*. *Counter for ships* is a borrowed meaning, likely owing to the connection between these vessels and sea birds.
[Full Kanji Etymology List]