According to RAW on familiars for Wizard/Sorcerer/Witch
Skills: For each skill in which either the master or the familiar has ranks, use either the normal skill ranks for an animal of that type or the master's skill ranks, whichever is better. In either case, the familiar uses its own ability modifiers. Regardless of a familiar's total skill modifiers, some skills may remain beyond the familiar's ability to use. Familiars treat Acrobatics, Climb, Fly, Perception, Stealth, and Swim as class skills.
So, if the Wizard/Sorcerer/Witch gains a skill point in linguistics, so does the familiar.
Can the familiar learn to speak common (or any other language) in this way?