TD&H
Speaking personally I have always used boffin as opposed to scientist or engineer to indicate just what you suggest - respect.
In my book all boffins are scientists but not all scientists are boffins. Boffins are totally dedicated to their work, care not what they look like (although may still be smartly dressed these days) and may behave in excentric ways when judged by those who 'conform' to establisment norms. Above all they do what they do for the benefit of knowlege and the project rather than the boss or promotion. Boffins are above such things. Way above.
JF