How do you write Robby in Gaelic?

There isn't a single, universally accepted Gaelic translation for "Robby." Gaelic (which refers to both Scottish Gaelic and Irish Gaelic) doesn't have a direct equivalent like English names often do. The best approach depends on the intended meaning and the specific Gaelic language.

* If Robby is a diminutive of Robert: You'd use the diminutive form of "Robert" in the relevant Gaelic language.

* Scottish Gaelic: `Ruaraidh` (ROO-ar-ee) is the full name, and diminutives could include `Ruairidh`, `Ruara`, or even `Rob` (though less traditionally Gaelic-sounding).

* Irish Gaelic: `Roibeárd` (ROW-bayrd) is the full name. Diminutives might include `Rob` or `Roibeardín` (though the latter is quite formal).

* If Robby is considered a name in its own right: You would likely transliterate it phonetically, resulting in something like `Robaigh` (pronounced roughly ROB-ee). However, this isn't a traditional Gaelic name and might sound somewhat foreign.

In short, `Rob` (Scottish and Irish Gaelic) or `Ruaraidh` (Scottish Gaelic) are probably the closest and most natural-sounding options, depending on whether you want a short form or a more formal, traditional sound. `Roibeárd` (Irish Gaelic) if using a more formal translation from Robert. Using a purely phonetic spelling feels less authentic.