free vs piggyback

free

adj
  • Not attached; loose. 

  • Of a rocket or missile: not under the control of a guidance system after being launched. 

  • Thrown open, or made accessible, to all; to be enjoyed without limitations; unrestricted; not obstructed, engrossed, or appropriated; open; said of a thing to be possessed or enjoyed. 

  • Without obligations. 

  • With no or only freedom-preserving limitations on distribution or modification. 

  • Without; not containing (what is specified); exempt; clear; liberated. 

  • Privileged or individual; the opposite of common. 

  • (of a morpheme) That can be used by itself, unattached to another morpheme. 

  • Unconstrained. 

  • Unobstructed, without blockages. 

  • Unattached or uncombined. 

  • Not imprisoned or enslaved. 

  • Unconstrained by quantifiers. 

  • Unconstrained of identifiers, not bound. 

  • Not arbitrary or despotic; assuring liberty; defending individual rights against encroachment by any person or class; instituted by a free people; said of a government, institutions, etc. 

  • Unconstrained by timidity or distrust 

  • Intended for release, as opposed to a checked version. 

  • complimentary 

  • Unconstrained by relators. 

  • Obtainable without any payment. 

  • Generous; liberal. 

  • Not currently in use; not taken; unoccupied. 

adv
  • Without needing to pay. 

verb
  • To make free; set at liberty; release. 

  • To rid of something that confines or oppresses. 

  • To relinquish (previously allocated memory) to the system. 

noun
  • A free transfer. 

  • The usual means of restarting play after a foul is committed, where the non-offending team restarts from where the foul was committed. 

piggyback

adj
  • On somebody's back or shoulders. 

  • Pertaining to transportation of goods where one transportation unit is carried on the back of something else. For example, a truck on a train. 

  • Attached or appended to something larger or more important. 

noun
  • An act or instance of piggybacking. 

  • The connection of one intravenous drip to another. 

  • A ride on somebody's back or shoulders. 

adv
  • On somebody's back or shoulders. 

verb
  • To transport (a lorry/truck) on a flatbed railway waggon 

  • To utilize "last-mile" wiring rented from a larger owner ISP by a smaller ISP. 

  • To obtain a wireless internet connection by bringing one's own computer within the range of another's wireless connection without that subscriber's permission or knowledge. 

  • To carry (someone) on the back or shoulders. 

  • To enter a secured area at the same time along with someone having authorized access; to tailgate 

  • To attach or append something to another (usually larger) object or event. 

How often have the words free and piggyback occurred in a corpus of books? (source: Google Ngram Viewer )