Question about vinegar in expressions

What does "vinegar in her voice" mean? It was said by a girl in a story about her sister, she envies her and feels bad in some way. The story is from the Bible.

Solution 1:

Word Reference quotes an unsourced reference relating to speech under their entry for 'vinegar' :

sour or irritable speech, manner, or countenance: a note of vinegar in his voice.

I found two metaphoric references to vinegar in the Bible, both from Ecclesiastes, all other references being to actual vinegar :

As vinegar to the teeth, and as smoke to the eyes, so is the sluggard to them that send him. Proverbs 10:26.

As vinegar upon nitre, so is he that singeth songs to a heavy heart. Proverbs 25:20.

Solution 2:

It's not real common, but definitely not unknown. "Vinegar" is tart/acidic, and makes a person speak with a sort of scratchy voice. But, more significantly, "vinegar", in one sense, implies a sourness of attitude, ie ill will.

So the person was speaking with a bad attitude, and you could almost hear it in the way she spoke.