sluggish

Sluggish comes from the English noun slug plus the suffix -ish, which traces back through Middle English -isch and Old English -isċ to Proto-Germanic *-iskaz and ultimately Proto-Indo-European *-iskos.

The facts here show only the combination of slug and -ish forming the adjective; no further shift in meaning is recorded.

The -ish ending links sluggish to any English word formed the same way, since that suffix's job — turning a noun into a descriptive adjective — traces back through the same Old English -isċ line.