I would like to say, "I am a grumpy dog," since I did not get my proper sleep last night. I have a few guesses about "grumpy", but these are only guesses. I looked up "grumpy" on Whitaker's words and found nothing. I looked up "irritable" and found stomachosus as well as acriculus.
Stomachosus canis sum. / Acriculus canis sum.
I wanted to know if either of these words are le mot juste. If not, what would you suggest?
There's nothing wrong with stomachosus, though it is not a very common word. Smith recommends, besides stomachosus, difficilis:
II. In partic., of character, hard to manage or to please, obstinate, captious, morose, surly: “difficiles ac morosi,” Cic. Or. 29 fin.; “moderati nec difficiles nec inhumani senes,” Cic. de Sen. 3, 7: “sunt morosi et anxii et iracundi et difficiles senes,” id. ib. 18, 65
That last reference also gives us iracundus:
I.irascible, irritable, passionate, choleric, angry, ireful, easily provoked (class.): “iratus potest non esse iracundus: iracundus non potest aliquando iratus non esse, Sen. de Ira, 1, 4, 1 (al. om. non before potest): ut non tantum iratus sit sapiens, sed iracundus,” id. ib. 2, 6, 3: “sunt morosi et anxii et iracundi senes,” Cic. de Sen. 18, 65: “iracundum esse in aliquem,” id. Planc. 26, 63: “adversus hostes,” Just. 7, 6, 15: “quemadmodum posset leniri, Sen. de Ira, 1, 1, 1: tale non est ira, sed quasi ira,” id. ib. 1, 2, 6: “leones,” Ov. M. 15, 86: “mens,” Lucr. 3, 296.—Comp.: “iracundior est paulo,” Hor. S. 1, 3, 29.—Sup.: iracundissimus, Sen. de Ira, 2, 6, 4; 2, 15, 1.
Acriculus is only found in Cicero's Tusculanae Disputationes, so personally I'd stay away from it, especially with iracundus paralleling grumpy so neatly.
In my first year of Latin in high school, we read a much simplified version of Querolus, about a very grumpy old man and his pot o' gold. It turns out to be post-classical, probably 5th century, but it tries to use classical vocabulary and style.
The word Querolus itself translates more directly to something like "the complainer", but it's quite close to what you seem to need (although it's a substantive). If you read the source text, then maybe there will be some interesting synonyms there.
