a propos
accidentally
apropos
apropos of
as it chanced
by a fluke
by accident
by chance
by good fortune
by hazard
by the by
by the way
casually
en passant
for example
for some reason
fortuitously
in passing
in some way
obiter
par exemple
parenthetically
perchance
somehow
somehow or other
speaking of
unpredictably
Bentley
coincidentally
continentally
developmentally
differently
environmentally
experimentally
fundamentally
gently
incrementally
intently
mentally
monumentally
ornamentally
temperamentally