c. 1200, "state of being worthy," from Old French dignite "dignity, privilege, honor," from Latin dignitatem (nominative dignitas) "worthiness," from dignus "worth (n.), worthy, proper, fitting," from PIE *dek-no-, suffixed form of root *dek- "to take, accept."
From c. 1300 as "an elevated office, civil or ecclesiastical," also "honorable place or elevated rank." From late 14c. as "gravity of countenance."
It forms all or part of: condign; dainty; decent; decor; decorate; decorous; deign; dignify; dignity; diplodocus; disciple; discipline; disdain; docent; Docetism; docile; docimacy; doctor; doctrine; document; dogma; dogmatic; doxology; heterodox; indignance; indignant; indignation; indignity; orthodox; paradox; synecdoche.
It is the hypothetical source of/evidence for its existence is provided by: Sanskrit daśasyati "shows honor, is gracious," dacati "makes offerings, bestows;" Greek dokein "to appear, seem, think," dekhesthai "to accept;" Latin decere "to be fitting or suitable," docere "to teach," decus "grace, ornament."