frank1
  
  adj.
  - candid and honest. ▸sincere or undisguised: ![]()  frank admiration. 
- Medicine  unmistakable.
Derivative
  
  Etymology
  ME (in the sense ‘free’, also ‘generous’): from OFr. franc, from med. L. francus ‘free’, from Francus (see Frank: only Franks had full freedom in Frankish Gaul).
 
  
    
frank2
  
  v.
 stamp an official mark on (a letter or parcel) to indicate that postage has been paid or does not need to be paid. 
▸historical sign (a letter or parcel) to ensure delivery free of charge.
n.
 a franking mark on a letter or parcel.
Derivative
  
  Etymology
  C18: from frank1, an early sense being ‘free of obligation’.