An Etymological Dictionary of Astronomy and Astrophysics

1. To have actual being or reality; to be.
   

2. To have life; to live.

Etymology (EN): M.E., from O.Fr. exister, ultimately from pr.p. of L. existere/exsistere “to stand forth, appear; to exist, be;” from → ex- + sistere “cause to stand,” from PIE *sta-, cf. Pers. istâdan “to stand,”
→ state.

Etymology (PE): Hastumand budan, from Mid.Pers. hastumand “existing, existent,” from hast, ast ‘is" (infinitive hastan, astan);
O.Pers. astiy; Av. asti “is;” O.Pers./Av. root ah- “to be;” cf. Skt. as-; Gk. esti; L. est; PIE *es-, + euphonic -u-, + -mand possession suffix, → -ist, + budan “to be,” to become;" Mid.Pers. butan “to be ,become,” from O.Pers./Av. bav- “to be; become, take place,” Av. buta- perf. ptcpl. pass., bavaiti “becomes,”
Skt. bhavati “becomes, happens,” bhavah “becoming; condition, state,” PIE *bheu- “to be, come into being, become;” cf. Gk. phu- “become,” phuein “to bring forth, make grow,” L. fui “I was” (perf. tense of esse), futurus “that is to be, future,” Ger. present first and second person sing. bin, bist, E. to be, O.Ir. bi’u “I am,” Lith. bu’ti “to be,” Rus. byt’ “to be.”