library name
Dated computing term for the name of a library (collection of routines or data). In modern contexts, ライブラリ名 is more common.
In this program, you call a function by specifying the library name.
Modern equivalent; 登録集名 is an older, less common term.
Compound of 登録 (registration) + 集 (collection) + 名 (name), likely a calque or older translation of 'library name' in computing.