According to Reb Hirsch (Ethymological Dictionary of Biblical Hebrew, Ed. Matityahu Clark), halal means "radiate" (1. praising; shining. 2. boasting. 3. being hypocritical. 4. revealing God's presence. 5. radiating light. 6. reflecting light. 7. shining at weddings. 8. borrowed brilliance). Hope this will help a bit.
Yours sincerely
Martin Schroeder