A friend sent me, by way of a St Patrick's day greeting, a little shamrock icon. But no sooner had it arrived and gladdened my first-generation Irish heart, than she wrote again, worrying that what she had sent me was, in fact, a clover icon. (Separate question: Who would bother to make a clover icon?)

Continuing this column's unexpected botanical slant, I wondered how closely related the two things are, and of course where the word shamrock comes from. Anyone who's ever been sent a shamrock by an Irish grandmother will know it to be quite different to English clover, being much smaller. But is it true, as some killjoy American tells us, that shamrock is just young clover? Well, yes and no.

First, the etymology. Seamar, pronounced "shammer" is the Irish for clover, and óg the Irish for young. Seamar óg, which gives us shamrock, by way of earlier variants such as shamrog and shamrogth, is therefore simply young clover or little clover. As to botany, shamrock and clover are names for various species of three-leaved plants, known imaginatively to botanists as trifolium. But the OED says that clover usually means "meadow clover", trifolium pratense ("three-leaves of the meadows") while shamrock usually means yellow clover, trifolium minus ("lesser three-leaves"). In sum: there is a distinction you can make if you want, but if you prefer just to pin some young clover to your lapel, no one will think any the less of you.

This week's happy accident, meanwhile, is my discovery of the phrase "drowning the shamrock" - to go drinking to celebrate Saint Patrick's day. Which I certainly intended to do, even before I knew there was a term for it.