The official term for "desktop" as an adjective is "deisce" (FR 211, desktop computer, ríomhaire deisce, meaning a computer designed to sit on a desk). This term is unobjectionable, though I find "inneall bóird" much more natural.
However, we also have "desktop" as a noun, meaning the screen imagined as similar to a physical desktop, with icons (representing unopened folders) and windows (representing opened folders). It is especially applied in the situation where there are no open windows, leaving the desk relatively bare. For this use of "desktop", we are offered only "deasc" (FR 211), which hardly captures the idea.
This idea of the desktop is close to the basic meaning of "clár". And, with a little bit of licence, we suggest "lom-chlár" for "desktop". Humour is often used in making computer terms in English (e.g. underflow, virtual reality), but it must be used with restraint, as the resulting term is liable to be unhelpful in suggesting the concept. But I think there is no danger in this instance.
It will be interesting to see if Irish computer users will rise to the joke, or whether we will be asked where are the bits meaning "desk" and "top".
The suggestion of "deilín" for "password" is another exercise in attempted humour, but one with which I am less satisfied.