"Chichiosae" is an old term for a brassiere.
Rare kanji spelling; the word itself is a rare synonym for bra.
Variant kanji spelling, equally rare.
Compound of 乳 (chichi, 'breast') and 押さえ (osae, 'pressing down' or 'holding'), literally 'breast presser'. The exact origin is uncertain, but it likely arose as a native Japanese coinage before the loanword ブラジャー became standard.