Words from:

   Rosemary and Rue
by Seanan McGuire
An October Daye Novel

extemporizing

I was extemporizing wildly, but I had no way of knowing that. [Loc 4882-43]

extemporize: verb

(used without object)
1. to speak extemporaneously.
2. to sing, or play on an instrument, composing the music as one proceeds; improvise.
3. to do or manage something in a makeshift way.

verb (used with object)
4. to make or devise extempore*.
5. Music. to compose offhand; improvise.

* extempore: on the spur of the moment; without premeditation or preparation; offhand

diurnal

[Bane] of night people to deal with—those rare souls who chose a diurnal existence. [Loc 2441-42]

diurnal: adjective

1 .of or pertaining to a day or each day; daily.
2. of or belonging to the daytime ( opposed to nocturnal ).
3. Botany . showing a periodic alteration of condition with day and night, as certain flowers that open by day and close by night.
4. active by day, as certain birds and insects ( opposed to nocturnal ).

undine

[Searching the water for] an undine named Lily. [Loc 2442]

undine: noun   1. any of a group of female water spirits described by Paracelsus*.

Note: Paracelsus first used word  undine in his 16th century alchemical work, Liber de Nymphis, sylphis, pygmaeis et salamandris et de caeteris spiritibus.

János Thorma Fiddling Gypsy Couple:
http://commons.wikimedia.org/wiki/File:Thorma_Fiddling_Gypsy_Couple_1935.jpg

The Rooster Crows, artist unknown
http://commons.wikimedia.org/wiki/File:The_Rooster_Crows.jpg

Henry Fuseli Title: Hagen und die Undine von Danubius
http://commons.wikimedia.org/wiki/File:Johann_Heinrich_F%C3%BCssli_041.jpg