Etymology
From Middle English *goodwille, good wille, possibly from Old English *gōdwille (compare gōdwillende (“well-pleased”)). Compare also Scots guidwilly, guidwillie (“displaying goodwill”). By surface analysis, good + will.
Cognate with Scots guidwill (“goodwill”), Middle Low German gūtwille (“goodwill”), Old High German guotwilligi (“goodwill”), Old Danish godvilje (“goodwill”), Icelandic góðvilji, góðvili (“goodwill”), Icelandic góðvild (“goodness”).
The sense "thrift shop" is a genericized trademark of the US-based chain Goodwill Industries.