English: Marshal Blucher's Official Report of the Operations of the Prussian Army of the Lower Rhine.

Quoted by Edward Cotton, A Voice from Waterloo, 5^th edition, 1854, chapter X.

p.154 (...) In the middle of the position occupied by the French army, and exactly upon the height, is a farm called La Belle Alliance. The march of all the Prussian columns was directed towards this farm, which was visible from every side. It was there that Napoleon was during the battle ; it was thence that he gave his orders, that he flattered himself with the hopes of victory ; and it was there that his ruin was decided. There, too, it was, that, by a happy chance, field-marshal Blücher and lord Wellington met in the dark, and mutually saluted each other as victors. In commemoration of the alliance which now subsists between the English and Prussian nations, of the union of the two armies, and their reciprocal confidence, the (p.155) Field-Marshal desired, that this battle should bear the name of La Belle-Alliance.
By order of field-marshal Blücher,
General Gneisenau.

By the time this report reached Lord Wellington, the Waterloo Despatch ►(File:18_June_1815_–_Victory_at_Waterloo_–_The_Waterloo_Despatch.jpg) was already sent off to London, and the name Battle of Waterloo went down in History.
In Germany however, the name Belle Alliance was preferred, and used e.g. at Berlin-Kreuzberg ►(File:Berlin,_Kreuzberg_Denkmal_–_South_face.jpg), or on the battlefield itself : ►(File:18_June_1815_–_Victory_at_Waterloo_–_To_the_Prussian_Army,_Epitaph.jpg).

One depiction of the historic meeting : ►(File:18_June_1815_–_Victory_at_Waterloo_–_"About_ten_o'clock,_...".jpg) – among many others.

Above the front door, a tablet ►(File:18_June_1815_–_Victory_at_Waterloo_–_La_Belle_Alliance,_replacement_tablet.jpg) recalling that famous meeting (which, in fact, took place further south), being a replacement of the ca. 1815-1820 original ►(File:18_June_1815_–_Victory_at_Waterloo_–_La_Belle_Alliance,_original_tablet.jpg) now preserved in the Wellington Museum at Waterloo.