oncer

noun4

1. •
   (literary) A person who does something once.

   • Could he but once see Nature as / In truth she is for ever, / What oncer would not fall in love? — 1944
2. •
   (informal) A person with whom one shares a single sexual encounter, a one-night stand.
3. •
   (informal) A single sexual encounter between two individuals, a one-night stand.
4. •
   (informal, historical) A one-pound note.

noun1

1. •
   (slang) A fan of the television series Once Upon a Time.

   • And fun because, well, he gets to interact with “Oncers” at fan events like PaleyFest and Comic Con […] — 2013