dome vs helmet

dome

noun
  • head, oral sex 

  • A prism formed by planes parallel to a lateral axis which meet above in a horizontal edge, like the roof of a house; also, one of the planes of such a form. 

  • A geological feature consisting of symmetrical anticlines that intersect where each one reaches its apex. 

  • A person's head. 

  • A structural element resembling the hollow upper half of a sphere. 

  • Any erection resembling the dome or cupola of a building, such as the upper part of a furnace, the vertical steam chamber on the top of a boiler, etc. 

  • Anything shaped like an upset bowl, often used as a cover. 

verb
  • To shoot in the head. 

  • To give a domed shape to. 

  • To perform fellatio on. 

helmet

noun
  • The glans penis. 

  • The hood-shaped upper sepal or petal of some flowers, as of the monkshood or the snapdragon. 

  • A naked shield or protuberance on the top or fore part of the head of a bird. 

  • The feature above a shield on a coat of arms. 

  • A hard, protective head covering, typically part of armour. 

  • A contemptible or stupid person. 

  • The upper part of a chemist's retort. 

verb
  • To cover with, or as if with, a helmet. 

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