There are a number of theorems or lemmas or mathematical ideas that come to be known as eponymous
*tricks*, a term which in this context is in no sense derogatory.
Here is a list of 10 such tricks (the last of which I learned at MO):

- the Whitney trick
- the deTurck trick
- the Cayley trick
- the Rabinowitsch trick
- the Klee trick
- the Moser trick
- the Herglotz trick
- the Weyl trick
- the Karatsuba trick
- the Jouanolou trick

**Edit: List augmented from the comments and answers:**

- the Eilenberg–Mazur swindle
- the Parshin trick
- the Atiyah rotation trick
- the Higman trick
- Rosser's trick
- Scott's trick
- the Craig trick
- the Uhlenbeck trick
- the Alexander trick
- Grilliot's trick
- Zarhin's trick [For any abelian variety $A$, $(A \times A^{\vee})^4$ is principally polarizable.]

**Further Edit.** And although my original interest was in eponymous (=named-after-someone) tricks, several non-eponymous tricks have been mentioned, so I'll gather those here as well:

- the determinant trick
- the kernel trick
- the W-trick

Some of those listed above do not yet have Wikipedia pages (hint, hint—Thierry).

I (JOR) am not seeking to extend this list (although I would be incidentally interested to learn of prominent omissions), but rather I am wondering:

Is there some aspect or trait shared by the mathematical ideas or techniques that, over time, come to be

named"tricks"?

I am aware this is a borderline question; feel free to close if it unduly distracts.