The second line of the text in Lübeck / Tallinn says "See here the mirror". The word has formerly been read as "spectel" i.e. spectacle, but after the restoration one can see, that it says "spegel".
The oldest known dance of death, namely the danse macabre in Cimetière des Innocents (picture to the right) refers to itself as a mirror:
En ce miroer chascun peut lire,|
Qui le conuient ainsi danser.
Saige est celuy qui bien si mire
In this mirror everyone can read,|
that he will dance likewise.
Sage is he who mirrors himself well.
Des dodes dantz is often referred to as speigel des dodes (mirror of death) because of a quote from the work:
Den speyghel des dodes, de hir na volgende is;|
Alsus halet de doet uns allen, dat is wys.
The mirror of Death that here is following;|
Thus Death takes us all; that is certain.
The dance of death is a reminder that even the mightiest man and the fairest maiden may in short time become a banquet for maggots: Your fat king and your lean beggar is but variable service — two dishes but to one table, as Death demonstrates to the (vain) women in the samples below on this page.
But the dance of death is also a mirror of society. The long row of dancing humans represent all stations in life and anyone can find himself in the line and mirror himself in how he would react to Death and how he should have prepared himself (I say 'he' because only 2 of the 24 dancers in Lübeck are women).
In Lübeck the mirror-metaphor is taken one step further than in any other dance of death since Lübeck itself appears twice in the background (see the notes here and here).
The participants do not appear in a random order but follow a strict hierarchical sequence - starting with the pope, who as God's substitute is the mightiest mortal, and finishing with the tender infant.
The dancers are alternating representations of ecclesiastical and secular society. This is true, both for the painting in St. Mary's Church and for Des Dodes Dantz, but not for Dodendantz, which is further proof that Des Dodes Dantz is older than Dodendantz. However, this sequence is apparently broken a few places:
The empress follows the emperor. There were no women in the original danse macabre, but in Lübeck the emperor is duplicated. The empress doesn't represent any particular rank but rather all married women. Death accuses her of "female sins" such as presumptuousness and fondness of finery, whereas the empress laments that she shall not see her children grow up.
Between the mayor and the usurer, comes the physician. The physician is regarded as ecclesiastical because he has studied. The same thing is true for the student in Des Dodes Dantz. The physician is a scientist — unlike the lowly barber-surgeon or sawbones who works with his hands and therefore counts as a craftsman.
This may not sound convincing, but take a look at the text from Berlin's dance of death. Here we have a sharp distinction between clerics and laity - with all 14 clerics to the left of Christ and here we find the doctor with the urine glass among priests and monks.
The dance ends with young man, young woman and child. Here we are no longer dealing with classes. The maiden represents all unmarried women (as opposed to the empress).