der Tick
quirk
A strange habit, an eccentricity, or an odd personal trait.
Sie hat den Tick, ihre Bücher immer nach Farben zu sortieren.
She has the quirk of always sorting her books by color.

quirk / tic
Loading your saved state.
quirk
A strange habit, an eccentricity, or an odd personal trait.
Sie hat den Tick, ihre Bücher immer nach Farben zu sortieren.
She has the quirk of always sorting her books by color.

'Der Tick' (quirk / tic) does not mean the same thing as the English 'tick'. It does not refer to a mark (check mark), nor to the sound of a clock. It describes a strange habit, an involuntary movement, or a very small amount.
Er hat den Tick, ständig auf sein Handy zu schauen.
He has the quirk of constantly looking at his phone.
You can recognize the meaning from the context: 'Den Tick haben, etwas zu tun' (to have the quirk of doing something) means a habit. 'Einen Tick' followed by an adjective, e.g. 'einen Tick zu laut' (a tiny bit too loud), means 'a little bit'. A 'nervöser Tick' (nervous tic) refers to an uncontrolled body movement.
Sei bitte leise, die Musik ist einen Tick zu laut.
Please be quiet; the music is a tiny bit too loud.
When 'Tick' (quirk) describes a strange habit, the fixed expression 'einen Tick haben' (to have a quirk) is often used. The habit itself is frequently described with a 'zu' + infinitive construction.
Mein Professor hat den Tick, während des Redens immer auf- und abzugehen.
My professor has the quirk of always pacing back and forth while speaking.
In the meaning 'ein bisschen' (a little bit), the fixed form 'einen Tick' (a tiny bit) is used like an adverb. It comes directly before an adjective or comparative to express a small increase or deviation.
Kannst du das Salz bitte einen Tick weiter nach rechts schieben?
Could you please move the salt a tiny bit farther to the right?
Using 'einen Tick' (a tiny bit) for 'ein bisschen' (a little bit) is very typical of spoken colloquial German. It is used less often in formal or written texts.
Ich komme einen Tick später, weil der Bus Verspätung hatte.
I'll arrive a tiny bit later because the bus was delayed.
something / somewhat
'etwas' and 'einen Tick' can both mean that a difference is only small. 'etwas' is neutral and fits almost anywhere when something is a little more, less, or different. 'einen Tick' is more colloquial and often emphasizes a very small difference, especially in comparisons. 'einen Tick' sounds more natural when you are describing a subtle change, for example in color, temperature, or behavior.

Für meinen Geschmack ist die Suppe einen Tick zu salzig.
For my taste, the soup is a tiny bit too salty.
In der Pause wird der Raum etwas ruhiger.
During the break, the room becomes somewhat quieter.