HAGGARD
SWELTERING
HOGBACK
DOWNDRAFT
BIBLIOPHILE
DEVILMENT
FLEET
IRTRONS

Several options:

One - as Penny says, they all consist of letters

Two - specifically, they all consist of letters, derived from the Greek, in standard use today.

Three - they are all taken from the English language

Four - they all mean different things

Five - I haven't spoken any of them out loud in conversation during the last year.

Six - they have all been listed as having something in common in a puzzle at http://perplexus.info

Seven - none of them could sensibly be used to describe a bucket

Eight - they all fit into this stupid sentence: A fleet of haggard bibliophiles rode hogback into a sweltering downdraft of devilment-cauing irtrons.

Nine - they can all be used to create a moronic list of things that they have in common that you've just wasted valuable seconds of your life reading.

There's probably some sensible things as well, but frankly I don't have time for them.