“Tongue” is here a metonym referring to a person who gossips, as well as a literal part of the body.

The adjective “lascivious” is an example of hypallage or transferred epithet. It isn’t the comments themselves that are lascivious but the subject of those comments. In short, the Young Man is sleeping around.

The lines can be summed up to mean: ‘People who gossip about you can’t say anything bad without it turning out good’. Shakespeare creates a moment of tension as the reader waits to be told the reason.

Line four begins with an exclamatory “O!”, suggesting high emotion. The poet doesn’t condemn the young man but instead seems almost joyful that the youth’s beauty hides vice: “O! in what sweets dost thou thy sins enclose!” Here, “sweets” is used in the archaic sense of sweet nature or beautiful appearance.

The sonnet opens with the exclamatory statement “even your bad traits are made beautiful by your loveliness!” A canker is a destructive plant disease, related to our modern word ‘cancer’. There is tension in these lines, since it is implied that the young man hides a sinful nature, and that the shame could blemish the Young Man’s name. The poet’s attitude is rather paternal and he lectures the young man on the deceptiveness of the appearance he projects.

Shakespeare uses a simile, comparing the young man to a “fragrant” but diseased rose that could be damaged if left unchecked.

Shakespeare uses the adjective “budding” as a double entendre, meaning developing in reputation as well as growing in beauty like a flower.

The final metaphor is the knife, which used clumsily will be damaged or “lose his edge”. The phallic implication is unmistakable. So, Shakespeare ends on a note of humour.

Seem pretty young? Don’t act surprised: Swift himself was packed off to Trinity College Dublin when he was only 14.

Founded in 1584 by a Puritan statesman called Walter Mildmay. Today it’s one of the wealthiest and most academic colleges in Cambridge. This choice of college perhaps implies a left-wing, Protestant upbringing for the young Gulliver.