followers you know
Followers you know (sometimes ambiguously called followed by) is a Twitter feature shown on user profile pages when logged in that displays both a number and a sampling of users you follow who follow the profile you are viewing.
Examples of "Followers you know" in the Twitter UI.
Twitter pop-up profile
Pop-up profile preview, note highlighted "Followed by ", then names of (up to) 3 of those followers, then "and 89 others", all of the text preceded by (up to) 4 of those followers (in icon form).
Twitter full profile
Full profile view, note "92 Followers you know" with (up to) 10 of those followers (in icon form).