The Proto-Indo-European word *ar(e)-ĝ-
Word *ar(e)-ĝ-
Meaning glittering, bright, white, fast
See also Linear B: a-ku-ro ‘silver’
Cappadocian Greek: αρέ ‘quickly, immediately’
Cappadocian Greek: çynoar ‘eagle’
Thracian: arzas ‘white’
Greek: άργιος ‘swift, fast, white’
Greek: αργέστης ‘shining, brilliant, white, bright’
Tocharian B: ārkwi ‘white’
Armenian: arcatᶜ ‘silver’
Greek: άργυρος ‘silver’
Phrygian: ΑΡΓΥΙΤΑΣ ‘lamia, daemon’
Hittite: ḫar-ki-iš ‘white, bright’
Ancient Macedonian: ἄργος ‘field, plain, valley’
Synonyms *k̂euk-, *bʰel-, *gʷʰh₂í-, *h₄elbʰós, *bʰris-~bʰers-, *gʷhaidrós, *h₁ōk̂-us, *h₂erĝ-, *h₂r̥ĝ-rós, *k̂eigh-, *k̂weitos, *(s)koitrós, *bʰelh₁-, *h₂ēhₓtró-, *h₂r̥ĝ(u)-, *hₐeĝilos, *leukós

Other words that might be of interest
*dheu-1 ‘dust, smoke, vapor’, *bʰer- ‘brown, shining’, *dʰel- ‘light’, *dhuh₂mós ‘smoke’, *h₂éhₓtr̥ ‘fire’, *h₁égni- ‘fire’, *h₃és-no- h₃és-i- ‘ash’, *leuk-; lóuk-o- ‘bright light’, *meldh- ‘lightning’, *sneudh- ‘cloud, mist’, *séhₐul ‘sun’, *temó- ‘dark’, *tón-r̥- ‘thunder’, *reudh- ‘light red’, *kwapor ‘smoke, steam, heat’, *péh₂ur ‘fire’, *h₂eidh- ‘kindle, ignite’, *bʰéh₂(e)s- ‘light’, *bʰéh₂tis ‘light’, *bʰel- ‘shine’, *bʰerhₓĝ- ‘shine, gleam’, *bʰleg- ‘shine, burn’, *dh(o)ngu- ‘dark’, *g(e)ulo- ‘fire, glowing coal’, *ĝher- ‘shine, glow’, *h₃meigh- ‘drizzle, mist’, *h₄elh₁- ‘burn’, *hₐeidh- ‘burn, fire’, *hₐel- ‘burn’, *(hₐ)mauros ‘dark’, *(hₐ)merhₓgʷ- ‘dark’, *hₐewes- ‘shine’, *hₓn̥gʷnis ‘fire’, *kenhₓis ‘ash’, *kenk- ‘burn’, *ker- ‘burn’, *tómhₓes- ‘dark’, *wer- ‘burn’, *k̂ehₐu- ‘burn’, *kʷap- ‘seethe, smoke’, *k̂seh₁- ‘burn, singe’, *lap- ‘shine’, *leip- ‘light, cause to shine’, *leuk- ‘shine’, *mer- ‘shine, shimmer’, *merk- ‘darken’, *nébʰes- ‘mist, cloud, sky’, *(s)kand- ‘shine, glitter, moon’, *skótos ‘shadow, shade’, *sk̂ōyh̥a ‘shade’, *(s)m(e)ug(h)- ‘smoke’, *(s)plend- ‘shine’, *sweid- ‘shine’, *swer- ‘darken’, *ghromos ‘thunder, groan’, *h₂éhₓōs ‘ash’, *lóuk(es)- ‘light’, *(s)tenhₓ- ‘groan, thunder’