(n): a large and densely populated urban area; may include several independent administrative districts
(n): edible purple or red berries
(n): any of numerous small and pulpy edible fruits; used as desserts or in making jams and jellies and preserves
That's a good question. The OED gives the etymology of saskatoon as being from the Cree words "misâskwatomin" (the shrub) (for which it cites Lacombe, Dictionarie de la langue des Cris), and "misâskwat" (the berry).
The OED (at least the online version) does not list "Saskatchewan" (probably because it's proper?), but is clearly a Canadian/Native Canadian place name. One might surmise that both terms at least came from a similar root language, if not that one term came from the other. And there endeth my minimal knowledge, so if someone else knows, have at it!
Is this word related to Saskatchewan?
Canadian name of the shrub or small tree Amelanchier canadensis (var. alnifolia), and its fruit, also called June-berry, shad-berry, and service-berry.