lavabo vs piscina

lavabo

noun
  • A ritual involving the washing of one's hands at a church's offertory before handling the Eucharist. 

  • A trough used for washing at some medieval monasteries. 

  • The small towel used to dry the priest's hands following the ritual. 

  • A lavatory: a room used for urination and defecation. 

  • A washbasin, particularly (Christianity) the one in a church used in the ritual. 

piscina

noun
  • A drained basin near a church's altar for the disposal of water from liturgical ablutions. 

  • A basin or tank, especially one for holding fishes or for growing aquatic plants. 

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