"woman pregnant for the first time," 1879, from earlier use in German, from Modern Latin, from Latin primus "first" (see prime (adj.)) + gravidus "laden, full, swollen, pregnant with child" (see gravid).
late 14c., "first, original, first in order of time," from Old French prime and directly from Latin primus "first, the first, first part," figuratively "chief, principal; excellent, distinguished, noble" (source also of Italian and Spanish primo), from Proto-Italic *prismos, superlative of PIE *preis- "before," from root *per- (1) "forward," hence "in front of, before, first, chief."
The meaning "of fine quality, of the first excellence" is from c. 1400. The meaning "first in rank, degree, or importance" is from 1610s in English. Arithmetical sense (as in prime number, one indivisible without a remainder except by 1) is from 1560s; prime meridian "the meridian of the earth from which longitude is measured, that of Greenwich, England," is from 1878. Prime time originally (c. 1500) meant "spring time;" the broadcasting sense of "peak tuning-in period" is attested by 1961.
"pregnant," 1590s, from Latin gravidus "loaded, full, swollen; pregnant with child," from gravis "burdened, heavy," from PIE root *gwere- (1) "heavy." Related: Gravidity. Gravidation "pregnancy" is attested from mid-15c.
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<a href="https://www.etymonline.com/word/primigravida">Etymology of primigravida by etymonline</a>
Harper, D. (n.d.). Etymology of primigravida. Online Etymology Dictionary. Retrieved $(datetime), from https://www.etymonline.com/word/primigravida