What is a Southpaw Word™?

This is in the spirit of the What is a Word/Phrase™ series started by [JLee][2] with a special brand of [Phrase™][3] and [Word™][4] puzzles.

If a word conforms to a special rule, I call it a Southpaw Word™.

Use the following examples below to find the rule.

And, if you want to analyze, here is a CSV version:

SOUTHPAW WORD™, NOT SOUTHPAW WORD™
FAST, QUICK
SCREW, NAIL
SWEET, SOUR
TREATS, TRICKS
AVERTED, WELCOMED
REAR, FRONT
CREED, MANTRA
@45266, COMMUNITY

• Is it Southpaw or lonely? thanks – Omega Krypton Apr 3 at 2:51
• How on Earth do people catch my mistakes within the span of 30 seconds?! Thanks, @OmegaKrypton. – user45266 Apr 3 at 2:52
• With the last line as it stands, this is geographically-biased; in particular, here in the UK @45266 is not a Southpaw Word. – Gareth McCaughan Apr 3 at 10:18
• @GarethMcCaughan Is that because of (n qvssrerag xrlobneq ynlbhg)? – user45266 Apr 3 at 14:55