bra vs breaststrap

bra

noun
  • An item of underwear worn to support the breasts. 

  • One of the two vectors in the standard notation for describing quantum states in quantum mechanics, the row vector; the other (column) vector being its complex conjugate, the ket. 

breaststrap

noun
  • An oblong application supporting the mammaries of a human female 

  • A piece of horse tack for preventing the saddle from slipping backwards. 

How often have the words bra and breaststrap occurred in a corpus of books? (source: Google Ngram Viewer )