I agree. Perhaps 'vap' is short for 'vapid' (lacking taste, zest, or flavor). So 'vapping' may mean 'vaping mediocre e-liquid'.
LOL! I'm sticking with the more tradition perversion of 'vapor'
Etymology: Middle English
vapour, from Anglo-French
vapor, from Latin, steam, vapor
Date: 14th century
1 : diffused matter (as smoke or fog) suspended floating in the air and impairing its transparency
2 a : a substance in the gaseous state as distinguished from the liquid or solid state
b : a substance (as gasoline, alcohol, mercury, or benzoin) vaporized for industrial, therapeutic, or military uses;
also : a mixture (as the explosive mixture in an internal combustion engine) of such a vapor with air
3 a : something unsubstantial or transitory