Thielen: Last Name Origin and Family Crest
Thielen is best understood together with Thiel: both are German spellings of a single family name.
Local scribes, dialects and emigration all left their mark on how the name was written. Thielen adds -en to the root of Thiel, a common way of forming related surnames.
Heraldry is personal: arms associated with the Thiel surname were borne by specific families, and sharing the name does not mean sharing the blazon. Research your Thielen family history with a full surname report and painted coat of arms.