From Dictionnaire historique et bibliographique de la Suisse (1921):
ADANK - Family originally from Maienfeld (canton Graubünden), now extinct there, as well as Chur and Tschappina. Branches of the family also have citizenship in Fläsch, Schiers, Luzein, Zizers and Zürich.
STECHER - Separate families originating from Seewis (canton Bern), Tarasp and Fuldera (canton Graubünden). A branch in Sarn had political influence in the 17th and 18th centuries.
The online version of the Swiss telephone directory has 233 entries for Adank and 207 for Stecher - neither surname is very common.