Which is that point? Well...It is the Symmedian Point, aka Lemoine Point.
Peter Baptist [1] wrote a paper on its history but I haven't seen it.
The name of Grebe is sporadically mentioned in the Triangle Geometry
Literature.
Sortais & Sortais write:
<q>
Le theoreme de Grebe (1ere demostration 1847): une construction du point
de Lemoine.
K: point de Lemoine du triangle ABC. K est parfois appele point de Grebe
du triangle ABC. [2, p. 160]
</q>
Honsberger writes:
<quote>
In Britain and France this point [:Symmedian Point] is also called the
Lemoine point, and in Germany it is also called Grebe's point.
You will find the early history and an extensive account of this point
in two articles by John MacKay [3, p. 57]
</quote>
The references cited are [4,5], but I haven't seen them either.
Also, why is it symbolized with K?
References
1. Peter Baptist: Ein Beispiel aus der Dreiecksgeometrie im 19. Jahrhundert:
der Lemoine Punkt.
In: Binder, Christa (ed.): Mathematik - A la mode? Tendenzen und
Modeerscheinungen in Forschung, Lehre und Stil. II. Oesterreichisches
Symposium zur Geschichte der Mathematik, Neuhofen an der Ybbs, 22. bis 28.
Oktober 1989, Kurzfassungen der Vortraege, Ergaenzungsband.
Wien: TU Wien, Inst. f. Techn. Math., 1989.
2. Yvonne at Rene Sortais: La geometrie du triangle. Exercices resolus.
Paris: Hermann, Nouveau tirage, 1997. ISBN: 2-7056-1429-4
3. Ross Honsberger: Episodes in 19th and 20th Century Euclidean Geometry.
MAA, 1995. ISBN 0-88385-639-5
4. John MacKay: Early History of the Symmedian Point.
Proccedings of the Edinburgh Math. Soc., XI, 1892-93, p. 92.
5. John MacKay: Symmedians of a Triangle and their Concomitant Circles.
Proccedings of the Edinburgh Math. Soc., XIV, 1896, pp. 37 - 103.
Antreas