*magh- Look up *magh- at Dictionary.com
Proto-Indo-European root meaning "to be able, have power." It forms all or part of: dismay; deus ex machina; may (v.1) "am able;" might (n.) "bodily strength, power;" main; machine; mechanic; mechanism; mechano-; mage; magi; magic.

It is the hypothetical source of Sanskrit mahan "great;" Greek mekhane "device, means," mekhos, makhos "means, instrument;" Old Church Slavonic mogo "to be able," mosti "power, force;" Old English mæg "I can."