I've been on Linux desktop (Mint) for over a decade now. My company uses O365 for email, as did the organization before them.
I use Thunderbird with several add-ons: Mailbox Alert, Owl for Exchange (paid), Provider for Exchange ActiveSync, and TbSync. I honestly couldn't tell you which one or ones I find most useful - it's been so long since I've installed them, I don't remember which addon provides which functionality. My most recent install was Owl, for calendaring and because things got a wee bit fucky with O365 servers for a week or two last year. I have Thunderbird set to collect addresses when I reply to users. You can have it query AD for contacts, I think, but it tends to be a wee bit slow.
On my Android phone, I use the default Google Calendar app, and the Gmail app to query O365.
I believe it's come from "based god", which referred to a god that appeared on earth.
Of course, it's been 10 years since I heard it used in that context, and assuming it hasn't evolved since then may be wrong...