Quarrelsome means always ready to argue. A quarrelsome neighbour, quarrelsome and difficult, quarrelsome by nature.
It describes a settled disposition rather than a mood, which is why it is such a heavy thing to say about somebody. The -some ending means tending towards, as in troublesome and burdensome.
1adjectivequarrelsomeAlways ready to argue.
“The two quarrelsome brothers could not sit at the same table without fighting.”
quarrelsome is a quality.
Quarrel plus -some, the ending meaning tending towards.
From quarrel + some.
Etymology from Wiktionary, CC BY-SA