As a noun bimmy
is a sennet whip.
As an adjective dimmy is
(dated) somewhat dim; dimmish.
bimmy
English
Noun
(bimmies)
A sennet whip.
References
* CorPun - Royal Navy Glossary
dimmy
English
Adjective
(
en adjective)
(dated) somewhat dim; dimmish
- Dimmy clouds. — Sir Philip Sidney.