That's the From Gambit. It is said to be unsound, but then so are the Latvian Gambit and Elephant Gambit, and in real life those aren't too bad, especially at nonprofessional levels of play.
(p. 503)
BIRD'S OPENING
(1 P-KB4)
POPULARIZED by the English master Bird towards the end of the
nineteenth century, his attack is rarely tried by modern masters because
it affords White too slim a grip on the centre. In Germany and Holland
it is known as the Dutch Defence with White. Today it is played only by
outright "devotees" who want to follow a set
strategy, well known to them, in order to avoid
surprises. 1 P-KB4 is an attempt to control
K5 and other vital dark squares, but it is non-
developing, slightly weakens the King's field,
creates some piece disharmony and fails to give
Black enough problems. But it does lead to an
eccentric equality.
Schlechter's line (col. 2) easily holds the
balance, but other replies are equally satisfactory.
Col. 1 is Capablanca's analysis. Col. 3 is the
modern treatment for Black, a sort of Queen's Indian Reversed.
From's Gambit (cols. 4-5) is a violent attempt to wrest the initiative.
Although considered unsound, it generally discourages a lot of players
from playing the Bird--instead of a quiet build-up, they immediately
find themselves on the defensive! But White can generally hold the
gambit pawn. Lasker's 4 ... P-KN4 (col. 4) is considered the main
line, although recent games revert to Schlecter's 4 ... N-KB3 with
varying degrees of success.
Evans, Larry, and Walter Korn. 1965. Modern Chess Openings, 10th Edition. New York: Pitman Publishing Corporation.
Any suggestion? Is from Gambit a sound reply to the Bird?