Detailed explanation: what is "dayspring"?

Solution 1:

The word used to be familiar to many English people from the Bible passage known as the Benedictus which is used in Morning Prayer in the Book of Common Prayer. It is from Luke 1 verses 68-79. Verse 78 reads Through the tender mercy of our God, whereby the dayspring from on high hath visited us. In modern Bible translations the word is given as dawn.

The derivation is fairly self-evident; the beginning of the daylight, as a spring of water may be the beginning of a river.

http://www.finedictionary.com/dayspring.html

Solution 2:

Exact meaning, with a link to the meaning in a dictionary.

The OED (which I think is pay-walled, so I can't post the link) defines the word as a synonym of "dawn" and "daybreak", with the addition that its later use is chiefly poetic or figurative.

Information about where dayspring came from and where it was first used.

The first attestation is in the 1382 Wycliffite Bible as a translation of Latin aurorae in Job 38:12:

"Whether […] thou […] hast shewid to the dai spring his place"

The word itself is a compound word consisting of the nouns day and spring. The latter is derived from the verb to spring, which has one of its meanings listed in the OED: "Of dawn, morning, daylight, etc.: to appear, to become perceptible; to appear over the horizon or in the sky". The earliest attestation of spring in this sense is from the beginning of the 14th century:

"Al þe day & al þe niȝt, Til hit sprang dai liȝt." (from "King Horn", c1300).

Solution 3:

The 1382 Wycliffe Bible translates Job 38:12 as:

Whether aftir thi rising thou comaundedist to the morutid, and hast shewid to the dai spring his place?

"dai spring" means "dawn" in this verse.