The second one is charging hourly. We tend to prefer hourly fees on projects that are particularly open ended or very small scope. Our hourly rates are currently between $60 and $120 per hour depending on who is doing the work.
The word sonder exists, though. It means to probe, and in a more specific use, to test the depth of something. The word sound (as in the water feature) is a cognate, both related to the Old English sund meaning to swim, or the sea. I can't really think of an English equivalent that's specific beyond mere awareness.
The word 'Darth' is a variation of the word dark. Vader: Vader means 'father' in German and Dutch, which could possibly have been a hint for the major spoiler to come. Another possible theory is that 'Vader' means invader the same way sidious and insidious are correllated..