There are a number of words in Shakespeare’s plays and poems which are deceptive to modern ears. They may seem familiar words but, in fact, camouflage a quite different meaning lost to modern English. In Linguistics, these words are called False Friends.
A False Friend is a word which has kept its form but has strayed from its original sense (or was a completely different word) so that the modern English word is false when compared to the original sense or word. Shakespeare likes to extend the wordplay further by often deliberately using words in their older senses. Consider the following words:
Modern: someone you are in a sexual relationship with, usually illicitly
Lover as friend precedes the modern meaning by a little over a century, with both dating back to the Middle English period. Shakespeare, however, punster that he is, uses lover almost exclusively in the old sense. If you do not know what he means, some Shakespearean situations can sound quite awkward, to say the least. Lorenzo, for example, fervently puts a plug in for Antonio to Portia as ‘a lover of my lord your husband’ (The Merchant of Venice, III.iv.7).
Modern: a person you know well, love and regard
Shakespeare: (primarily) lover
Friend is an Old English word which appears in texts as early as Beowulf; it derives from the Proto-Germanic frijōjanan and is cognate with the verb ‘to free’. It started with the sense we know today, with a slightly extended application to someone we hold in regard or a relative. This generalized sense, too, is encountered in Shakespeare and creates a pun or two. Now that you know what Shakespeare has in mind, you are clued in when Lady Capulet tells Juliet to stop crying, ‘So shall you feel the loss, but not the friend / Which you weep for’, and Juliet replies that she is weeping for her beloved — not the relative, ‘Feeling so the loss, I cannot choose but ever weep the friend’ (Romeo & Juliet, III.v.74-7).