Querulous
Etymology
From Latin querulus, "full of complaints, whining," from queri, "to complain or lament" — the same root that gives us "quarrel." The Latin word applied both to complaining people and to the plaintive sound of complaint itself. English inherited both nuances: querulous can describe the habit of grumbling and the whiny tone it comes in.
adjective · /KWER-uh-lus/
Habitually complaining, often in a whining, peevish tone.
What it names
The fretful, grievance-filled manner of someone for whom nothing is ever quite right, and who says so at length.
Example
From the back seat came a querulous stream of "Are we there yet?" and "It’s too hot."
Related idea
Petulant flares up in sudden fits of pique; querulous is a steadier, more chronic register of grievance — endless low-grade complaint.